I have to agree with Thermo, there are no hard and fast rules concerning income tax. IR35 is a particularly thorny piece of legislation. Setting up your own LTD company is no guarantee that your not gonna get clobbered. Fortunately HMRC introduced IR35 is order to try to extract loads of tax from Y2K IT contractors mainly, however, after y2K and the dotcom debacle, the revenue hasn't really seemed up for a fight as the number of IT contractor4s plummeted, so most people get away with it. Put it this way I've contracted for the same company for 10 of the last 11 years and have only been IR35'ed on one occasion, however that's no guarantee, it really depends on the wording of the contract, how aggressive you are with HMRC, how aggressive they are with you.
If you pay a reasonable amount of tax (i.e don't take it all in dividends), don't completely over egg your expenses (a little bit of creativeness here is tolerated) then you should be alright...... Probably