I love vinegar on things but walking around with your own dressing in a bag is a bit much.
The only thing the OP posted that I would regularly eat for lunch is probably the tuna and sweetcorn, but that is just because I'm not heavily into red meat I would eat the English breakfast or the pie only on a rare occasion and I wouldn't usually put meat on a jacket potato- beans, cheese, tuna, coleslaw, prawns are all OK.
There is a vegetarian shop near where I work that sells quiches, samosas, bajis, etc. so I sometimes have those for lunch.
On the weekend I might go to the pasty shop around the corner and get a ciabatta with seafood on it or something similar.