RedBagMan wrote: "Make sure you don't stitch yourself up regarding overtime" - wonder what he meant
It's typical veiled bullying, mate. Forget about it, laugh it off. Learn to say no much more firmly next time.
As regards your question, it's up to you. I would advise you not to not just for the reasons already given (money-wise) but for your own mental and physical well being. Having a day off will leave you rested and in a much better frame of mind. If you work six days a week and do half a walk every day, you threaten to reach a point where your mind and body is constantly in work mode, and the only thing you're going home for is to wait for work the next day. I initially always used to work my day off, but now I never do. Why should I? It's my day off, it's implied that I take it rather than being half-bullied half-connived into working it. It's the same with half-walks. I'll do them when I can be arsed and when I'm not doing anything.
But they can get frakked if they think they're doing me a favour. And the moment anyone implies that by not taking overtime I am somehow committing some grave offence, that's when the deal is off completely - no more overtime, no nothing. I'm on a 25-hour contract, if you want me to do more then give me a 30-hour contract. Otherwise, I'll do extra work on my terms.