I did try to dig out the contract just now to see if I had a digital copy of it, but I don't think I do. It's likely to be a two decade old printed copy instead. I think you need to talk to a lawyer rather than trying to do this on the cheap. Your lawyer has your interests at heart, no one else does. If you're a member of a union (Prospect being a good one for digital workers) then they will have lawyers you can consult for free.