I'm currently being made to work overtime for time in lieu. Can I be forced to work for TOIL instead of pay?

I am a Lorry Driver so my shift usually carries an indetermined ETA in order to clock off at a specified time. Since I am contracted to complete my work, unless I bring part loads back undelivered I may not be able to get back within my basic hours. The thing is, I have written to my boss saying I do not want to work for TOIL, only for pay. If he can't pay me I'd rather not work it, but he refuses to take me out of TOIL and says I'll be in breach of contract if I finish my shift without completing all my work. No terms and conditions have been set out or new employment particulars given. Is this legal, is there an avenue I can use to force my position?