NB: Those 28 "include" bank holidays. It used to be a 20 day mandatory minimum, which was meant to be 20 days + bank holidays, but unscrupulous bosses were including bank holidays in the 20, so some people were only getting 12 days "real" holiday. (Days they could pick).

So now it's a 28 day minimum, of which 8 are usually bank holidays and 20 free to pick.