As someone who contracts in the UK, I'd say it really depends on how much you're making and for what duration. If you're going to make £10,000 on a three month contract you're probably better off just registering for self assessment. I did this for a while when I was making around £28,000/annum because it was the most tax effective and easiest solution in my case. Also accountants are expensive.

If you're making £60,000+ you're probably going to want to set up an LTD company, but at that point you're really best off talking to an accountant and discussing your options.