My thoughts:
5. Blue Stilton Cheese on...anything - absolutely love Blue Stilton, but way out of my price bracket in Thailand (that is my assumption, but I've never actually priced it.
4. Jamie Oliver’s Spelt and Quinoa - no idea what it is. I guess I've lived in Thailand too long. Doesn't sound like my cup of tea.
3. A Packet of Crisps - is this a British thing? Regardless of what you call them, I thought it was a universal snack. However, Sea Salt & Aspall Cyder Vinegar crisps from Fairfield Farms - never heard of them

2. Fish and Chips - yay, this sounds very British, but then they go and spoil it all by adding creamy tartar sauce. i've used fish and chip shops all over the UK (you don't get a name like Big Boy without putting in a little effort

1. Tea and Scones - can't disagree that this is British, but not something I'd go out of my way to find here in Thailand. Certainly not my number 1.
Of the top 5 listed above, the only one I'd go out of my way to buy here is 2. Fish and Chips.
Where is the steak and kidney pudding, bangers n' mash, roast beef and Yorkshire pudding, chicken tikka masala etc., etc.?