TLDR: breeders can now, under the current exceptional circumstances, deliver puppies to their new owners. They should have sent you plenty of video evidence of the puppy with its dam so that you can be assured that you not buying from a puppy farm.
More details:
The Kennel Club yesterday released new guidance for animal-related businesses. You can find it here.
It looks as if it was produced in consultation with DEFRA as it is linked to from this page (see under 'short-term emergency advice for breeders'), where it is stated that 'The Kennel Club and other animal welfare experts have worked with Defra to produce short-term emergency advice for breeders, to help protect the welfare of puppies already bred.'
There is also advice there about socialisation during lockdown and so on. I hope this cheers up those of you who were looking forward to adding a puppy to the household in the near future.