Had to have a giggle at the subject I've also wondered that same thing, I'm not sure and probably very wrong but I think a bimble is for small bubs and a bumble is the next size up but as I said I've probably got that wrong
See that's where I am confused! Basically I just went onto easypeasy.co.uk and they have Bimbles up to size 2! I have read a little bit and they are called QD as in quick dry but I honestly can see naff all difference!! however you can get pretty pastel colours in the Bimble! lol
AHA! the Bumble is only birth to potty, the Bimble is trimmer and available in sizes as well as BTP wish I'd known that before I bought the Bumble as it is cheaper for me to get one that isn't BTP. Well unless I save for that maybe of another baby lol!