I got lucky when I found a local store that sells American and Australian goodies in the UK, americansweets.co.uk, I am hooked on twizzlers and pop tarts, plus I can get some of the rarer timtams, although tesco do have a lot of them now. Hubs loves reeves and the vanilla cola. My best buy is old bay, that stuff goes with everything!!
More awkward to find are choco pies, South Korean heavenly treat, a bit like wagon wheels but better. There are a few Korean supermarkets around but they are all at least an hour away.