"Also as others have pointed out.. If they class me as an employee Ill be looking for pension contributions, and will be invoking the working time directive when told I need to work more to get projects in early."
I think there's a precedent for this about 10 years or so ago. On the whole the contracting world didn't take kindly to a contractor nuking the client even if they thoroughly deserved it but the thought of having to cough up for employee benefits might concentrate the client's mind when it comes to assuring HMRC that this really is a contract for services.