No worries, answering my own question, there's a picture showing the prices on their website: https://www.raspberrypi.org/app/uploads/2019/02/Pi-Shelf.png

It's 32£, which is less than on amazon.co.uk (currently 33.95£, varying between 33 and 36 over the last month). I'm guessing it's pretty good.

You can occasionnally find them for less on chinese websites, but I haven't seen a deal in a while, and you need to wait at least 3 weeks to get one; which is pretty much the opposite of brick-and-mortar store.