I must be weird, but I've actually spent a lot of time thinking about how differently-sized bread is here in the UK, versus in the US!
In the US, pre-sliced bread is basically all the same size - a loaf is about 12-15 inches long, each slice is about a half an inch thick, and a slice is basically square-shaped - about 4.5 inches by 4.5 inches. Roman Meal = Nature's Own = Wonder Bread = Home Pride = pretty much everything else, size-wise.
Here in the UK, just in the pre-sliced, pre-packaged breads (not counting the bakery loaves), you can get anything from Kingsmill Toastie (thick, giant rectangular slices - a loaf is around 12 inches long) to Hovis Wholemeal (regular, small, squared slices - a small loaf is around 6 inches long). We usually buy Kingsmill Medium White for me and either Hovis Wholemeal or Warburtons Wholemeal or Premium Brown for DH. Just look at the difference!
(I can sympathise with your boyfriend, as when I can't get Kingsmill I usually buy Warburtons Farmhouse, which is much smaller - I'll eat two sandwiches instead of one, but I don't complain about it!
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