I know what you mean. I have got to the point where i don't even try to eat out on sw anymore! The only takeaway/cheap option that seems to be available is jacket spud and beans - bleeuurgh!!!! (or a salad which doesn't touch the sides with me). I try and take my own food to work where i can- usually leftovers from the night before in a tupperware. Much nicer than dry potatoes!
try a sandwich with either chicken, ham or tuna and ask for no butter and no salad dressing. add salad to pack it out and make sure its on wholemeal bread - this should hit the spot!
I always opt for a gammon steak with a jacket and salad. I also take my jar of Hellmans extra light mayo with me, or some laughing cow light cheese triangles if im having a jacket potato with baked beans.