Just thought I'd update you all on the situation today!
Took Ben (dad) to RSPCA and he is indeed still entire. They were extremely apologetic about the whole mess up and have agreed to castrate Ben (again) on Monday. Obviously they can't spay Holly (mum) yet until babies are older and when we know if she's pregnant again or not, but I'm just relieved they are happy to get this done for us (as it's not cheap! They are also going to find homes for the babies so that is also out of our hands! We want to keep one of them and (for £30) they will neuter and vaccinate for us. Successfully I hope!
Meanwhile I have brought Ben in the house until he is infertile! RSPCA said probably best to leave mum and babies where they are used to. They are in a Hutch within a shed and babies appear warm, cozy and deep in the nest. Too deep to get a photo! Two of my dogs are great with rabbits but one is a little ott with wanting to chase things! So gotta keep him out of the same room! Ben seems pretty settled already in his luxury holiday villa!