Tis a good point actually. I do feel guilt at buying from shops that sell pets.
Online frustrates me, as I have had so many replies along the lines of "we don't post to Northern Ireland" or "We post to Northern Ireland with an extortionate postage charge". Not all sites do this, but enough to make shopping around a pain in the !!!!
Closest we have to shops selling pet food but not pets is the Asda / Tesco / pet hut, and their selection of decent quality pet food doesn't tend to be great.
I'll be having another look on-line this week. I've seen a few recommended bunny foods on here that I know we can't get in any of the NI shops I'm aware off.