IANAL, this is also for UK. I as well was employed in the UK last year and had my contract checked by a lawyer. The contract contained few vague clauses regarding IP discovered during the term of the employment and some non competes with any business of the company or of the group companies. The lawyer confirmed the only safe route would be to have an explicit agreement providing me IP ownership and entrepreneurial freedom signed by the company.
Then it depends what your relation is to the company. Do you want to tell them you have more ambitions than being a loyal employee ? If your bosses are a 'general' management and not a founder etc., I very much doubt you will achieve anything positive yourself. I believe these contracts are a norm here from what I heard as well. (I quit in the end before starting my venture).