Hi Laura,
Your situation sounds really awful! How has it turned out since you last posted?
As mentioned the lack of a contract isn't going to help legal situation, but even so it might be worth going to Citizens Advice since he was the one who didn't want to write up a contract.
At the moment any job is better than no job just to survive sort of thing, but like many have said here just get out there! Unfortunately from the sounds of the work you have been told to do there you won't have benefited much in terms of Portfolio work, however make some stuff up on your own; redesign some logos, make some adverts, just try and create a vast portfolio which essentially shows what you can do! That's what a Portfolio is after all isn't it?!
Anyway! I hope you find some proper work soon! You sound determined enough, it's just a shame you have been used in such a dodgy way! Not every where is like that!