I am very upset as I have just discovered that my Golden Retriever's brother and sister, who were bought by the same person have mated (accidently I understand) and there is now a litter of 7 puppies. Does anyone know what will become of them? Will they be disabled, disfigured ot have personality defects?

Don't panic! Although in this case careless, close mating like this can be used very successfully if both parents have similar good qualities and no major faults. It can, in fact, be much more successful than when the parents are completely unrelated. The offspring of any mating can only inherit the genes of their parents - a close mating cannot create genes that weren't already there. If both sire and dam were healthy and carefully bred, then the pups from this mating will be fine.
:)