:wave: Welcome to bunny ownership Alison! I bet you'll soon be addicted like the rest of us! You definitely do need to separate dad if they've been mating, as if he is still in with mum when she has any babies, they will mate again straight away and then she will have another litter 4 weeks later. So you immediately end up not with 'just one' litter, but with two!! By the time you discover the first litter, it will be too late to take dad out as they will probably have already mated again so you can't really wait and see I'm afraid. Because in the wild so many baby rabbits don't make it to maturity, they breed pretty much back to back and the parents have a very short lifespan too! They usually only nest build when a litter is nearly due, so if she doesn't produce very soon, then it's probably just a phantom - but she is now at that age where she could get pregnant that's no guarantee that she didn't get pregnant yesterday, or tomorrow.
Having two (or actually even one) litter in this way gives many problems I'm afraid - you could potentially have up to 7 or 8 babies in one litter, so potentially 10-15 out of two, which is many babies all needing somewhere suitable to live if they are staying with you, or good homes elsewhere - and there are already 67,000 taken into rescues every year so there are already too many bunnies
It will be harder than you might think trying to find people who will give them the sorts of homes you'd like them to, and you could potentially end up with the next set of babies at sexual maturity and at risk of breeding again and/or fighting before you're able to find homes for them.
If dad stays in with mum, if she gets pregnant again, she will be exhausted after having 2 litters back to back; feeding so many little ones takes an enormous toll on their bodies. It also means that you'd have to remove dad for about 3 months while those litters grow up. In that time, you could get him neutered and then you would be able to try and reintroduce him to mum again once all the babies have grown up - but at that stage they will have been apart for a long time and there's no guarantee that they would become friends at that point - which presumably defeats the object of you wanting to have a lovely pair of bunnies. The same is true even if you remove him now and she only has one litter, but obviously the time they need to be apart will be less.
I know it sounds like a wonderful idea to have some baby bunnies, but honestly, the best outcome for your bunnies right now would be that she is having a phantom pregnancy; rabbits in the wild don't have babies at this time of year because it's too cold - and they have nests underground which are relatively stable temperature wise. I think you are sensible to try and make it as cosy as possible for her. Personally I would advise that you book the boy in for neutering ASAP and hope for the best that she isn't pregnant, and that way it should be far smoother and easier to reintroduce them and have a lovely happy pair of bunnies as pets. It may also be worth taking the female in for the vet to see if they can palpate a pregnancy. If they can't, you could get her spayed at the same time and then the pair of them could go straight back together after their ops and live happily ever after