Back in Ibiza, SW2

There's something satisfyingly wrong about Mass, the huge club in Brixton which outside still looks like the imposing, old church it once was. Whether it's the ultimate act of blasphemy or just a sign that dance music is the modern opiate of the masses, drawing millions each weekend to worship at the new altar of the DJ's decks, it's an impressive sight to arrive at on a Saturday night.

If clubs are the new places of worship, then Ibiza is the clubber's ultimate pilgrimage site. A mecca for the biggest DJs and most spectacular live shows, the island offers sensory elevation on a scale rarely found anywhere else — with the added bonus of beaches and sun. Yet with the season now over and winter drawing in, memories of Balearic bliss are disappearing as quickly as the leaves off the trees.

Not, however, if Ibiza Underground has anything to do with it. Celebrating its first birthday tonight, the club brings the best in Ibiza entertainment to the heart of south London, attracting a fiercely loyal crowd of about 2,000 every month. What's more, unlike the White Isle's extortionate drink prices, buy your ticket and the bar is free all night long.

We arrive just after midnight and are surprised to find everybody else appears to be inside already, following an early start of 9pm (to make the most of the drink-all-night price) so we head immediately to one of the two main rooms upstairs. Jo Mills, a regular at Ibiza hotspots like Space, Pacha and dearly departed DC10, is playing dark, dirty house to a cavernous room crowded with clubbers dancing beneath white camouflage netting hanging from the ceiling. A spontaneous disco chant of "ooh, ooh" suddenly breaks out as the music hits a peak.

This is no jeans and T-shirt crowd. All around are smiling fluoro-painted faces and luminous accessories, giving the room a kaleidoscope of colour. There are rave rings and wristbands, shutter shades as worn by Kanye West, tutus and pop socks on the girls and Altern-8 style rave boiler suits on the boys. We even catch sight of someone wearing a gas mask as the sound of an air-horn pierces the air.

Despite the crowd the bar is surprisingly quick, thanks to a two-drink per person limit to stop any silly orders slowing the service. With vodka Red Bulls in hand, my friends JP, Mark and I take a quick seat in the chill-out area between the main rooms. "You can't knock it," says Charlie, 19, who has been to five or six Ibiza Underground parties before. "The people and colour keep me coming back. And you wouldn't think they could do it but they have proper spirits — Smirnoff and Southern Comfort."

The second room has a similarly impressive number of people in a retina-burning, rainbow attire. A huge cheer sweeps the multi-tiered room as Bimbo Jones plays Soulwax's remix of Gossip's Standing In The Way Of Control. Either side of the DJ booth are podiums, a live sax player in one and a dancer in the other handing out lollies. With much of the packed crowd still in their teens, there's plenty of youthful energy and excitement to sweep you along.

"I spent the summer in Ibiza," says Alex, 18, who works in a beauty salon and has had her face covered in stickers. "This is definitely the next best thing. Everyone is happy and the acts are great." Lauren, 21, from Bexleyheath, agrees. "It's cheaper and closer to home than Ibiza. And I like how people dress up crazily."

After a quick cig in the huge outdoor smoking area, where we admire a group of girls in PVC nurses' uniforms, we check out Babaloo. Normally a separate club in the basement of Mass, tonight it's open as the third room. With low ceilings and pillars, there's a great vibe as the melody of Café Del Mar, Energy 52's trance tribute to Ibiza, hits our ears. "The club's a great idea" says Lewis Coleman, also known as Studio B, who has DJed here before and is waiting to play. "It's wild and off-key which gives it a great atmosphere, though nothing touches Ibiza."

The great thing about free drinks — their freeness — also proves our downfall. By 3.30am we're tired and emotional. There isn't an Ibiza dawn to welcome us as we leave for our cab, just the bracing air of Brixton, but as I put my hand in my pocket, I realise I've spent nothing all night. And that would be a welcome break for anyone.

Ibiza Underground, third Sat each month; next 15 Nov. Early bird (until two weeks before) £30 girls, £40 guys; normal advance £35, £45; on door £45, £55. ibizaunderground.co.uk