Has the roar of the Celtic Tiger changed Ireland? Or is it something in the water

A temporary signpost alongside the causeway connecting Inchydoney Island with the mainland of County Cork announced in bright-red capital letters that Twohig's Hill was closed. Not knowing if the hill formed part of my route, nor whether I would recognise a "hig"' if I saw two, I ignored it and cycled on. At the end of the causeway, a couple of kilometres south of Clonakilty, two metal barriers were drawn across the entrance to a narrow lane. A marshall with a yellow bib was directing the sparse, Sunday-morning traffic around the corner, on to the coast road. The lane, winding up towards a farmyard, had been closed for the West Cork Motorcycle Club's Fourth Annual Hill-Climb. At the bottom of what was evidently Twohig's Hill stood a boxy caravan, its plain, grey exterior enlivened by a mahogany-stained, neo- Georgian back door. Alongside it, a white line had been roughly painted across the road. In the corner field, surrounding another caravan from whose side-window chips were being served, was the most catholic collection of motorbikes imaginable. There were smoky old two-strokes bearing numbers felt-tipped on to sticky labels, and 250cc bikes that looked as if they had spent their best years hustling messengers around the West End of London. There were tall, motocross machines and 500cc racers, one of which – to judge from the gashes in its fairing – had travelled quite long distances lying on its side. The riders, revving up or talking idly, were similarly assorted: most wore old black leathers, the trousers apparently hand-me-downs from larger men; but one was encased in a tailor-made, white leather suit that announced the rider's allegiance to Honda, Castrol and Ireland. I pedalled across to a picnic table from which a woman was selling programmes for the event. It listed the riders' names, bikes and home towns (Ballinspittle, Innishannon and Skibbereen, but more frequently Cork); it advertised the services of a local butcher, roofing contractor and "general draper", plus the forthcoming programme at Clonakilty's Park Cinema. As I flicked through the pages, the woman asked if I would like to have a run up the hill on my bicycle. "We'll time you," she promised.

For someone with no more previous experience of Ireland than 26 hours in Dublin, it is hard to place the country on a spectrum of possibilities that ranges from the authentic (age-old bar-and-blarney charm) to the entirely bogus (organised cameos based on a script provided by the Irish tourist board). Given that the economy is fondly referred to as the "Celtic Tiger" for its rampant growth, the possibility that Ireland still runs at the speed of a horse-drawn caravan seems remote. True, the West Cork Motorcycle Club entirely lived up to the friendly, unpretentious image; but it did cross my mind that as soon as I had cycled off along the coast road, someone would yell "cut" and the motorcyclists would hurry home, check that the Romanian guest-workers had milked the cows and then settle down in front of satellite TV.

Interested though I was to discover the truth about Ireland, that wasn't the purpose of the visit to Inchydoney. Nor, indeed, was the cycling: although one rarely hears a bad word about bike holidays in Ireland, my preference is to ride around in the warmth of southern Europe. But there are times when you can't just please yourself – and your wife's birthday is one of them. Leslie likes spas; and I had decided, after long study of a "Body & Soul" holiday brochure, to give her a long weekend at the Inchydoney Lodge and Spa. While she was being massaged, sprayed and wrapped in algae by its thalassotherapists, I'd explore County Cork by bike.

About 40 minutes' drive from Cork airport, the Lodge and Spa has a sublime setting. Inchydoney Island has not actually been an island since the 19th century, when causeways were built connecting it to the mainland. But the Atlantic still all but encircles the headland of Virgin Mary's Point, on which the Lodge and Spa was built three years ago. It is flanked on either side by endlessly horizontal beaches, with precipitous dunes stacked up to the east.

Unfortunately, the hotel and its associated apartments don't live up to the location, the cluster of white, four-storey blocks looking not unlike an out-of-town office development; and the best part of the site, out towards the headland, is devoted to a car park. (According to local bar talk the planning authority, having approved the design for the hotel, then had doubts about giving it too prominent a position and insisted that it be pushed back against the hillside.)

Inside, the public areas are pleasant, particularly the large guests' lounge; and the restaurant (whose €50 or £33 five-course dinner is exceptionally good) benefits from huge windows with sea views. The bedrooms have a solidly provincial flavour. The spa, however, largely met with Leslie's approval, especially the sizeable pool filled with warm sea water.

The spa's regime, thalassotherapy, is (as scholars of ancient Greek will have guessed) based around sea water. At high tide, a pipeline sucks water out of the Atlantic – happily, Clonakilty Bay is not on the shipping lanes – into the spa's storage tanks, from which it is drawn and heated for the treatments. Although the Victorians swore by it, bathing in sea water might seem to have become a less obvious health benefit with each marine-pollution scare; but Christian Jost, the French doctor in charge of the spa, assured me of the purity of the local supply, which is analysed every three weeks.

The virtue of sea water, Dr Jost explained, is that its constituent parts – vitamins, oligo elements, carbohydrates and so on – match those in blood plasma. Heat the water, so it can pass through the skin, and it will nourish the body tissues. I am no radiologist (unlike Dr Jost), but that sounded good to me; and the French and German health services are so convinced of the benefits of thalassotherapy that they often pick up the tab for patients' treatments.

Such has been the success of the Inchydoney spa that by the end of the year it will have expanded to twice its original size. Among those being treated there, women form the majority; but the proportion of men is increasing, thanks to the encouragement of their partners, said Dr Jost. Following this trend, I limbered up for the day's cycling with a quick body scrub (a bit like being sand-papered, to take the rough edges off your skin) and a dose of algotherapy ("the use of micronised seaweed mixed with warm sea water, applied to the body and then wrapped in a heated blanket to cleanse and de-tox the body", according to the spa's brochure). Good? Well, if you have difficulty sleeping, I recommend applying a layer of warm, green slime to your body, wrapping yourself in plastic, and lying under a blanket: it works like magic. And if you yearn to have your 51-year-old skin stroked by a woman murmuring "You're so soft," my advice is to get rubbed down with a mild marine abrasive.

Of course I only put my toe in the sea water. The next day, Leslie followed up her scrub and algotherapy with total immersion in the spa's "Relaxing Day" programme, which included massage, a Vichy marine shower (her favourite: you lie naked in a sort of tropical downpour while a therapist in his Speedos works you over with massage oil) and balneotherapy ("computerised heated sea-water baths with automatic multi-jets for hydro-massage"). Meanwhile, I set out to discover Ireland. What did I find? That Cork's empty, winding lanes are excellent for cycling; that its soft hills are being overrun with grim, gated pseudo-ranch houses, no doubt a by-product of the Celtic Tiger economy; that Clonakilty's triumph in Ireland's 1999 Tidiest Town competition has quite gone to its head, with floral displays hanging off every shop front, including a fast-food joint and the video-rental store; and that the West Cork Motorcycle Club was still roaring up Twohig's Hill.

A two-night 'Spa Indulgence' weekend break at Inchydoney Lodge and Spa (00 353 23 33143, www.inchydoneyisland.com) costs £590 with Erna Low (020-7590 1777); the price includes flights to Cork on Aer Lingus from Heathrow, Ryanair from Stansted or BMI from East Midlands, transfers to the hotel, half-board accommodation and six spa treatments. At peak weekends the price may increase owing to higher air fares