You can find the equality act here. The part that deals with ‘reasonable adjustments’ is section 20, and you can find it here. In addition to the legislation there is a statutory code of practice
The Equality and Human Rights Commission has helpfully provided guidance on what the law means for service providers that is written in plain English. You can find this here. The is also specific advice for shops and petrol stations; hotels, restaurants and pubs; hairdressers, barbers and hair salons; amongst others on the site.
If you are someone that has had trouble accessing services there is also a handy guide for you here.