When buying a Lab pup always ask to see the parents' green Hip dysplasia certificates. The current average score for labs is 15. A pedigree with multiple FT champs might be too 'hot' for a novice or pet owner as it's instinct will be to work, and if frustrated may become destructive.
Any dog's health records can be searched for on the Kennel Club website -
http://www.the-kennel-club.org.uk/services/public/health/search/If a dog is registered it may be entered in any Kennel club event such as dog shows, field trials etc. If it is not registered it may not be shown or trialled and progeny will not be registered either. Prices are therefore generally lower, although having said that, the current economic climate is such that there are a lot of pups on the market and therefore prices will be falling. I know there are currently over 100 German Wirehair pups on the market and rather more Cocker Spaniels.
Always see the Dam and if possible also the Sire of any pups. The registration certificate should be available with the pup at the time of sale as this process usually take around 3 weeks maximum if done by snailamil and can actually now be done online instantly. If a breeder has a number of different litters available at one time it is possible he/she is a puppy farmer - the Kennel club is trying to eradicate these over a period of time and is encouraging responsible breeders to become members of the Accredited Breeder Scheme (
http://www.thekennelclub.org.uk/item/203)
The majority of good breeders also have access to free insurance for the first 12 weeks in the pups new ownership, when it is most vulnerable.