Anywhere in the UK? At all?
I can't seem to find them except for the odd one of the odd size (I think we need M or maybe even S and I can't seem to find anything in those sizes).
Little boy is starting to say "poo" when he's doing/done one and point to his front area (ahem) and though he's not really showing huge signs of readiness we were thinking of getting a family toilet seat just to save a few nappies at home, at least.
These seem like the best ones from the POV that they are pretty absorbent if you can't be bothered forget to change him out of a trainer pant into a proper nappy for a nap/car journey.
I was also thinking about the Pop-In that say they take a "whole toddler wee" if that is actually true, though you'd still need to change him before a nap (which is a pain when he falls asleep in the car of course).