my biggest concern would be the possibility of asbestos in the artex. I've just done a yell search and there's only one company in Stoke that is listed as doing asbestos removal. I'll pm you the details. The Direct.gov.uk website also has some good information on there about asbestos.
If you pop into Tile Giant, they know a few regular tilers and would be happy to pass you the details of tilers in this area.
You will need an acrylic primer in order to prime the plasterboard. You would only need a moisture resistant board if the area is going to get soaked i.e. if it's a shower area. You'll be fine to tile on plasterboard once the primer coat is dry.
GRR