The British Shorthair does not require a lot of grooming because the fur does not tangle or mat easily. However, it is recommended that the coat be brushed now and again. The idea is to brush off topcoat not the undercoat.
Although common in North America, onychectomy (declawing) is rarely practiced outside North America and is considered an act of animal cruelty in certain other regions. We are, like many other pedigree cats breeders, against declawing. Cats, if provided, will gladly use scratch posts and leave your furniture alone. In fact kittens from our cattery will learn to use sisal rope scratch posts before they leave our home and move to yours. Clipping cat's claws is very simple and "Brits" are very patient animals. They will not like it but they will let you do it.
Provide the cat with a litter box that is big enough for it to fit inside with plenty of room to turn around and dig. Make sure that the litter box is in a quiet place to provide you cat with a sense of privacy and security. There are many different kinds of litter, choose one that your cat likes. Clumping litters make it easier to keep litter boxes clean. Scoop the litter box on a daily basis. If using a clumping litter, on a monthly basis, dump the old litter and wash the litter box out with soapy water. If using a clay litter, the litter should be changed out and washed on a weekly basis. Make sure to provide one litter box for each cat you own. Kittens may have a tough time getting into a large, deep litter pan and may need to be provided with a smaller version.