I have a subscription to
ancestry.co.uk which includes most of the England and Wales census returns for 1871, 1881 and 1891 and quite a few for 1901.
The site has an index (which leaves a lot to be desired) and links to images of the actual census documents.
It is quite expensive to get a subscription (about £90 per year I think)
There are ways to access the site for less
You can get a trial subscription for free - it lasts 14 days - but you MUST give credit card details in order to get the free trial - and if you don't cancel within 10 (not 14) days you will be charged for a whole subscription year - worth doing if you have lots of time to use your trial time in and remember to cancel in time!
For a free trial subscription type "Ancestry UK Free Trial" into Google or any good search engine for current links.
If you want a full year's subscription e-mail
support@ancestry.comand send them a useless CV offering to work for them.
They will refuse your offer but give you a 50% discount on a subscription for your effort (or - at least they use to, they gave me one four years ago which I still use - they may have caught on to the scam by now)
Alternatively, of course, there are hundreds of members of Rootschat who have access to Ancestry, who more than willing to do lookups, so just ask on this board.
Messages starting "1871 / 1891 lookup" etc are usually answered within 15 minutes of the request. Requests for earlier census lookups often go unanswered.