Please, please don't buy a kitten from anywhere. If you pay money to someone you are encouraging them to keep on breeding. There are far too many cats for the number of homes available, and every kitten born basically means that another cat in a rescue won't get a home, and either will get put down, or will take up a place that another cat in desperate need could have had.
Rescues are desperately busy but I'm sure they will get back to you fairly soon. Issey, who posts on here, works for Yorkshire Cat Rescue I believe, and I see you're in Yorkshire, so she may post.
Also look on www.catchat.org for details of the rescues in your area and some of the cats and kittens they have available. It is still kitten season so all the rescues are full to bursting with kittens, and also have them in foster homes, so please bear with it.
Small kittens are always happier in pairs and get very distressed when they're left on their own. So unless you are going to be able to be with the kitten for 24 hours a day then you would really be better off getting a pair. Either that or adopt a slightly older one, say five months or so.
We've had a few threads covering the things first-time cat owners need to consider. I'll post a few links in a minute.
Once the cat is old enough to go out having a cat flap makes life much easier. You can put cat flaps in double glazed doors, in walls, in windows...