Its worth calling the rspca if like you said the mums having the babies so frequently!
Once is an accident, maybe even twice if you didnt know the mum was pregnant and the dad got her pregnant again after birth- but for it to happen that often is just neglect in my opinion! I do beleive a lot of people really do have accidents, missexed rabbits, bad pet shops etc, but for this couple to know about the rabbit being pregnant, and not seperate him after she saw him mounting her again, its just wrong!
Bleeding is not a good sign, and id want it checked out by a vet, but i guess the owners wont do that. And as you said about him not being neutored before the birth- theyll probably put him back with her before he's infertile after his op- leading to another litter.
I think its soooo wrong that this happens, and worst of all people like the rspca and pet shops espeically dont provide enough information about mixed sexed rabbits- i bought my first mixed sexed buns not so long ago, and i was definately getting them neutored (which they have been now), but i had no idea they needed to be sperated from about 12 weeks, someone on here told me luckily!
Anyway, good luck with it all!