What is an 8.5 x 4.5in bread pan in UK lb based pan sizes?
Unfortunately sorting bread pans by loaf weight is very vague. A 1lb light and fluffy white sandwich bread might have about the same size as a 2lb heavy, dense wholegrain or rye bread. Also, do you expect your bread to rise really high over the rim or should that be more of a limit? In short, the size of "a 1lb bread" depends a lot on the kind of bread you have in mind.

A quick Internet check of pan dimensions from various manufactureres confirms that there is no standard size, it seems they vary by up to 50% in volume. 

So if your relative's wish list states a pan of a certain size, I suggets you go shopping equipped with a meassuring tape instead of looking for a certain "pound value".



Side note: Most 2lb pans are a tad bigger that the requested size and 1lb ones a bit smaller, but I found one sold in the UK by Williams Sonoma (what a coincidence!) that seems to have exactly the sought-for dimensions.