I am looking for another golden retriever and have seen several ads for puppies whose parents have individually scores below the breed average but if the sire and dams scores are added together they are well over 20. Is this relevant to the health of the progeny's hips? Never had this problem before as all my retrievers had joint parent scores of under 15. Also if the dam has a hip score of say 15 and the sire 8 is this an OK mating?

Adding the hip scores does nothing, what you want to do is pop on to the KC website, and research the hip scores behind the parents, grandparents etc.  Are there any instances where similar lines have produced problems?  Having a myKC account (which is free) also helps look through previous health test results.  There is also a tool called Estimated Breeding Value (EBV) on the KC website, I use it when looking through Labrador pedigrees.  Simply put, HD is caused by a combination of genes from both parents, so one mating could produce good hips, another mating could produce poor hips in progeny, that's why you need to look at what the lines are producing and not rely on the hip scores of the parents on their own.

I would also ensure both parents have been elbow scored - this appears to be more of a problem than hips

It would also be an idea to check out their eye test results, elbows and possibly Ichthyosis if it has been done. My friend has a girl affected with Ichthyosis and whilst it isn’t  really serious enough to affect her dog’s life, it can be quite unsightly at times depending on hormone levels. It’s also worth looking at to coefficient of inbreeding, came across one pup advertised recently which had a CoI of 35% which to my mind is too high. Apologies if I’m teaching you to suck eggs!!

Thanks for all replies. I had no problems choosing my previous retriever puppies as in all cases both dams and sires had very low scores of sub 10 but looking this time I noticed pairings of dogs with much higher scores and I started to be a bit concerned. I wasn't aware of the other places I could research so many thanks for the information.