There's a shop chain in Northern England, it's called Boyes, it is the BEST for this. Like, I don't think I've ever once gone into the Boyes in my tiny middle-of-nowhere town needing something weirdly specific (craft-related or otherwise) and not been able to find it.
Basic interfacing? Check. Really specific size and colour of safety eyes? Somehow also check. Net curtain to turn into a wedding dress, and a lavender heat pack for my grandma? That's also a check. Set of screwdrivers, a new pair of pyjamas and some back to school supplies? I'll give you three guesses.