Contractor pay

[sally1001]

I have just started a job whereby I'm a contractor. Some 'umbrella' company claimed to have been sent by the company i work for and said i must be paid through them and they manage my tax etc. not having been a contractor before i just went along with it and signed forms that were not explained to me. anyway, 2 weeks into the job i've just realise that I pay them to manage my taxes; it looks like about 10% of my salary! does anyone know what my rights are? now i've signed contracts am i bound for the duration of my contract even though it wasn't explained to me? can't i just manage my own money like normal contractors?
thx

[antiguru]

The contract should also say what the cancellation terms are. You need to read it carefully now.