Its hard to guess what's going to be available. I stocked high with Branston pickle, marmite and marmalade, only to find all three available everywhere. Custard? Not for me thanks, but decent thick cream is all but unobtainable outside NW Europe.

Cider - virtually unobtainable elsewhere (exceptions are North Spain, Canada, Australia, I don't count the French rubbish. The tinned UK stuff travels best). I became Mr Popularity in the WI with this, a refreshing alternative to cold beer. There just has to be market opportunity.