I sold a puppy to a family a week ago and today they have said they are not coping very well with the puppy, he is being noisy and their neighbours are complaining etc. I have said I am quite happy to take the puppy back, but my question is, should I offer a full refund? a partial refund? or no refund at all?
There is nothing physically wrong with the puppy, they were all checked by a vet prior to leaving their mum, and they are covered by 6 week free insurance.
please help advise me what is the best thing to do to keep everyone happy? I dont mind taking the puppy back, I have someone else who is interested in buying a puppy so I could find him a new home with them instead but what is the right thing to do? I havent had this happen before as all my pups usually go to forever homes :-(

Personally, I'd get the puppy back asap and give them a full refund at this stage.

If the puppy has only been gone a week and it comes back to you in the same condition that it left you then I would give a full refund

Your first priority should be the puppy.  It cannot be happy in that situation.  You bred it, you sold it (unintentionally I know) to the wrong home, so you owe it to the puppy to get it back and find a better home.  For goodness sake, just do it.  Give a full refund, stop dithering about how much money, you say you can re-sell it anyway so you won't be out of pocket.  The puppy should be your first priority not wondering about how much money you can keep.

Sorry if this sounds harsh, but living in an environment like that could well be detrimental to its future temperament, so it is important to sort things quickly.