The one thing I REALLY wish I could find in Scotland is saltine crackers. I've tried everything I can think of for a substitue, but no joy.
I miss 3 Musketeers and Butterfingers at times, but as I am not a regular candy bar gal, I can get over it easily enough.
There is a GREAT Mexican/American import store in Edinburgh (and one in Glasgow) that does Betty Crocker, Cheese-in-a-Can, Libbys Pumkin and lots more. I am sure there must be some great places similar throughout the UK.