There are some pretty good IR25 proof legal contracts out there. The key is to have a contract that defines your independence and that the way in which you operate with the client is very unlike that of an employee. Good examples are the ability to choose when and where you work, that you can work for other companies at the same time, and the fact that you use your own resources: http://www.contractoruk.com/contracts/wary_consultancy_contr...

For more information, and where to find a good lawyer who can firm up such a contract, try http://www.contractoruk.com/ir35/