Here in Switzerland it is illegal to own a single guinea pig.
If you have an older piggy who looses their mate, there are 'loan' schemes available when you take on a new friend for the bereaved piggy and then return it to the breeder when your own piggie passes away.
There are literally no piggies in rescue here, and the wait lists are long.
I think this is largely because all male guinea pigs are castrated between 2- 3 weeks of age, and immediately put back into the family group. This prevents accidental or irresponsible breeding, and means that unless you own a small animal license, it is literally impossible to get hold of an uncastrated male.
Breeders are licensed, and subject to yearly inspections - the standards are very high.
Whether you get your piggie from a pet shop or a breeder, you will be expected to provide proof of your set up and ownership of other piggies.
I was quizzed very thoroughly before being sold my pigs, and had to provide not only several photos of my pigs, but the contact details of the local vet and receipts to prove I had actually bought the cages pictured in the set up (and not just swiped a photo from the Internet I guess). It is quite hard to get hold of a single piggy,
and all breeders and pet shops will take back any animal that you an no longer care for.
C&C cages and fleece bedding are somewhat of a novelty here - our cage was visited by a lot of people when we first got the pigs.
Most guinea pigs are kept in wooden hutches on disposable bedding, and the few other people that I know who have guinea pigs, tend to bring them inside (or at least into an outbuilding) over the Winter.