Regarding the Monster Munch, is it the pickled onion ones or the ultra yummy beef ones that made a retro comeback in the last year or 2. For years you could only get that flavour if you bought the multi variety pack.
There's a Top Shop and Dorothy Perkins for the ladies and Top Man for the guys but the clothes may be a bit young I don't know. Holland and Barratt are a fairly recent arrival.
Cold Storage sell Walkers crisps 6 pack (mostly plain flavour) and they're about $10

That makes it nearly a quid per bag of crisps. The Cadbury chocolate mostly comes from Australia so tastes nothing like the stuff from Birmingham although every now and again there may be a little promo near the till selling some imported from the UK. I got Cadbury Mini Eggs last year and I was in heaven.
There's a shop called Candy Empire and they sell quite allot of chocolates and sweets from around the world with a nice hefty price tag. Found small (and I mean small) tins of Quality Street for $38. Not quite the 2 for a tenner you get back in the UK.
Oh, if you have access to a car, you could always hop over the border to Johor in Malaysia to get your fix of Tesco shopping.