How many Points are you on, hun?
If you're on big Points you could work some treats into your allowance, or save some up. Fish and chips from chippy is roughly 15 pts, and I think a Big Mac and fries would be something similar.
Otherwise, why not make your own burger? You can use extra lean mince but I like the Tesco Finest beef burgers, only 3.5pts with low fat cheese and relish, v tasty. You could make some chips in the oven. Also Young's do a nice chip shop style fish which is around 4-5pts.
Or maybe you could share with someone?