My meeting with Sir William Lawrence, chairman of Tourism For All, is proving problematic. As he emerges from a meeting at the Local Government Association (LGA) in Westminster's Smith Square, a pint at the nearby Marquis of Granby is out of the question as his wheelchair doesn't fit through the door. A moment of calm at St John's Church opposite Local Government House is also impossible, given the numerous steep steps and lack of a ramp.

Instead we head for a coffee in the LGA's first-floor café. That is, of course, having first negotiated the lift, a simple enough manoeuvre but one that entails fellow lift users side-stepping the wheelchair, trying to hold the doors open for us and mumbled apologies as we all try to squeeze into the confined space.

But Lawrence is used to the rigmarole. He was four when he contracted polio and has never walked since. A mini stroke following a problematic trip to China in 2004 further weakened his left-hand side. "I made a speech in Beijing one day and fell off the toilet the next morning," he deadpans. "Apparently it made The Guardian."

Formed in 1976 as Holiday Care, Tourism For All changed its name in 2004. Today it campaigns to raise awareness of accessibility issues as well as giving advice on disabled-friendly places to stay and visit around the UK. In October this year it will publish an updated second edition of Easy-Access Britain: The Guide to Accessible Places to Stay & Visit, which will include information for disabled people and their carers making plans to visit the 2012 London Olympics.

There are, according to the Disability Rights Commission, 10m disabled people in the UK - including half-a-million wheelchair users - who need information on places to stay. Currently, however, the National Accessible Scheme, which is managed by VisitBritain, the UK tourist authority, and Tourism For All, is so strict that, in London, for example, just two properties have been approved by inspectors - and they're both youth hostels.

"The Olympics and Paralympics are a great opportunity for Britain, as people have to change and they need a spur to make those changes," says Lawrence. "Clearly a large number of people will want to explore Britain during that time and they will find things are changing slowly. But I recently visited the Tower of London with my wife and the facilities for wheelchair users were appalling. Just an inexpensive track to cover the cobbles would make such a difference."

Lawrence regularly makes site inspections and cites some recent examples of good practice. English Heritage has installed lifts at Kenilworth Castle in Warwickshire, while the Royal Shakespeare Theatre in Stratford-upon-Avon is being partly rebuilt with lifts, so that wheelchair users can move around and get into the restaurant.

Since the advent of the Disability Discrimination Act, it has been illegal to refuse to serve somebody on the grounds of disability. Yet VisitBritain says only 2.5m disabled people actually travel regularly, making for a huge untapped market with enormous spending power. Tourism For All wants to see the UK tourism industry do more to make accommodation, destinations and attractions more accessible.

"What I want to see is understanding and belief within the travel industry that there is a market for accessible products. This largely untapped market will only start to travel once they have confidence to do so," says Lawrence.

But Andy Wright, managing director of Gloucester-based specialist tour operator Accessible Travel & Leisure, and himself a wheelchair user, says the National Accessible Scheme is too limited. "Facilities across the UK have improved significantly over the past 10 years," he says. "We need to revisit the grading system." Wright says there are many facilities that are to people with disabilities but fall short of the National Accessible Scheme's standards.

"We're about to invite the world's Paralympians to our country and we're spending £400,000 on a logo, so surely we can find some money to publish quality information."

Back in the coffee lounge it's time to say our goodbyes. Lawrence is planning a letter to culture and sport secretary Tessa Jowell about the potential problems of the new Olympic logo for people with epilepsy, while his wife is concerned that a parking fine awaits them. Westminster, it transpires, is one of several London boroughs that enforces a four-hour limit on the use of disabled parking bays - that's if you can even find one.

"I'm very organised when travelling but even I fall foul of the system sometimes," says Lawrence, heading for the lift again. "For example, VisitBritain recently invited me to attend the Excellence in Tourism Awards at Whitehall Palace. I drove 110 miles one way to get stuck at the front door. In the end I just turned round and went home again."

Tourism For All,

tel: +44 (0)8451-249971;

www.tourismforall.org.uk