The Disability Discrimination Act
The Disability Discrimination Act states:
Section III
19. - (1) It is unlawful for a provider of services to discriminate against a disabled person-
(a) in refusing to provide, or deliberately not providing, to the disabled person any service which he provides, or is prepared to provide, to members of the public;
These laws apply whether the nature of the site is commercial, educational, charitable or even your hobby. If you publish content on the world wide web in the UK you make a reasonable effort to ensure that content is accessible to all users, whatever their disability.