Ian, I suggest you take a trip to a register racing kennel, there are plenty around where you live, have a look at the conditions and the health of the dogs.
While there, familiarise yourself with the rules regarding the welfare of racing greyhounds, how all dogs under rules, have to be chipped and have personal ID stored by GBGB.
It is the duty of owners to have retired dogs rehomed, and any cruelty can be traced back via the dogs ID......heavy fines or imprisonment would be involved for animal cruelty.
I have been involved in the sport for fifty years and any ill treatment of dogs has been roundly condemned by all trainers and owners.