It's interesting that in a system set up by the Labour government in the late 1990s that in 2011/12, substantial tax and national insurance savings will continue to be made by a self employed person by forming a limited company.

Profit            saving
£10k               £ 299
£20k               £1,199
£30k               £2,099
£40k               £2,999
£50k               £4,257

This of course is before consideration to the cost of fulfilling obligations set by HMRC and Companies House to submit numerous returns.