It started with one watercolour. Twenty-five years on, every inch of Tim Sayer's small home is covered in works of art, from a Hockney in the loo to tribal figures in the fireplace. Just don't ask him about his overdraft ... By John Windsor. Photographs by Oscar Paisley
Most Brits would rather buy a new car or a carpet than a work of art. Not so, Tim Sayer, a 53-year-old BBC radio news journalist, who spends pounds 12,000 or more in a single year on artworks and is constantly in debt. He owes monthly part-payments of pounds 150 to pounds 200 to each of half-a-dozen art galleries. He is even working for free at next week's annual contemporary art fair, ART99.

Sayer will be in his element as an unpaid assistant for Blond Fine Art, one of his favourite gallerists. For him, five days of immersion among the exhibition's thousands of pictures and sculptures is the only form of narcosis capable of tempting him away from his own collection - 300 contemporary artworks that fill every inch of the walls and shelves in his two-floor flat in Highbury, north London. Having done a deal, he will pace around the flat with his new acquisition under his arm, looking a little demented, trying to find somewhere to stash it. He has resorted to hanging paintings on the ceiling.

There are Hockney and Tapies prints in the lavatory, a tiny Arthur Boyd landscape on the stairs, erotic Eileen Coopers in the bedroom and, in the sitting room, two elemental Ewen Hendersons beside three abstract Gordon Baldwin ceramics. A charcoal nude and a bright landscape by his late friend, William Mills, face each other across the room, tribal figures from Papua New Guinea stand in the fireplace, and a whirring automaton with gyrating telescope by Tim Lewis surveys the room from a corner. "It is a little crowded," he says.

The carpet is a slightly worn. He could easily sell a painting to pay for a new one. But he says, "Sod the carpet. And sod redecorating the outside of the house. Thank god, at least the roof's solid.

"If I see something I like I convince myself that I can afford it - even if it means not paying the water bill. I tell myself, stop being so bloody mean. Buy the stuff. I get so irritated by people who say that art is expensive. It is, but not compared with other things. They spend money on, say, an off-the-road vehicle, which will be a pile of rust in a few years' time. But I will still have my art."

His taste has become more abstract since his first purchase 25 years ago, a John Nash watercolour. But he clearly has an eclectic eye. Although he owns several drawings by Prunella Clough, several abstract oils by Maurice Cockrill, several Coopers and a host of Mills, most of the 120 artists in his collection are represented by a single artwork.

In the early Eighties, he started going for colour. Such are the vagaries of taste. Apart from that, what makes an artwork irresistible to him? "It's got to appeal to the head, heart and balls," he says. No mystery there, then.

Of the three standard rules for private collectors, he obeys two: see a lot of art, and get to know the artists. The third - take your time - he ignores. "I can't bear people who faff about and insist on seeing a picture six times. In any case, if you hesitate, then go back expecting to buy, in 80 per cent of the cases the painting has been sold."

When I met him, he had just returned from lunch with his bank manager. But he was far from hangdog. He had paid for the lunch, and the bank manager had seen his collection - and its potential as collateral. It is now worth about pounds 250,000. What did he pay for it? "God knows; I've never added it up."

In the past, when he has received letters from the bank about his overdraft, he has replied that he is about to sell some paintings. The overdraft is converted into a bank loan, the financial storm clouds gradually disperse - and the paintings remain unsold. "I do get sleepless nights and I do get nagged by Annemarie, my girlfriend. But so far I have avoided bankruptcy."

He buys only from "sympathetic" galleries - those that, unlike auction houses, will allow him time to pay. "Sometimes I am lucky enough to be offered a discount as well. If I buy direct from an artist's studio I always give them the price they ask, even if I have to pay over time - after all, they are not financially cushioned like galleries."

He fetches out a cardboard box. Frequent use has given it a patina of fingerprints. This is his file of gallery bills, recording his part-payments. "I hate this thing," he says. Among its contents, an account rendered by the Fischer Fine Art Gallery, acknowledging the last of his 24 monthly instalments for the Australian Arthur Boyd's little oil on board, River Landscape No. 3 of 1991 - a total of pounds 3,701.25 including 10 per cent discount. A sympathetic gallerist has scrawled a sigh of relief, "Aaaahhhh", across the account. During the repayment period it felt more like "Aaaarrrgggghh!"

Sympathetic galleries? Besides Fischer, Sayer buys from Blond Fine Art, Annely Juda, Art First, Austin Desmond, Purdy Hicks, Art Space, the Hart Gallery, the Belgrave Gallery, Flowers East, Graham Paton and Jason & Rhodes.

Does he buy for investment? "It's never entered my head. If it did, it would ruin the enjoyment. However, I'm sure I've never paid over the odds for anything"

ART99, 20-24 January, Business Design Centre, 52 Upper Street, London N1 (0171-359 3535).