Basically you build up your credit rating by being on the electoral roll, maintaining a bank account in good nick until they let you have a loan! Some cards like Capital One will allow you one with a small limit and HP on a car often has different acceptance criteria as the car would be repossessed if not paid for. The HP route is one a lot of people use but you will be paying extra for the credit as you will have to go to a company which offers the facility to those with adverse credit.
Getting a mortgage is not impossible for recently discharged bankrupts but again the subprime market would have to be used - and these are contacted through specialiat brokers and IFAs. If you look at http://www.mortgagebosss.co.uk you will find information on the kind of rates charged.
However, applying for credit shortly after discharge from bankruptcy will not send a great signal to the credit industry and applications will be recorded on the credit file. Basically the Enterprise Act 2002 gives people a fresh start but is not designed to allow them to run up credit again in the short term. The effects are going to stay on the credit file for six years and the longer that passes between discharge and the end of the six year period the more likely one will be offered a low level of unsecured credit.