I'm pretty near in Bracknell, I always use Apex models in Crowthorne http://www.apexmodels.com/index-flash.php. Although you may or may not be aware that lots of Halfords stores (including Bracknell) carry HPI cars and spares. There is a list of which stores on this page http://www.halfords.com/opd_product_details.asp?id=18425&type=0&cat=279 .
As for tracks, none better for a Savage than the Max bash track in Guildford. Here is the site, it also has a good forum: http://www.maxbashing.com/
The nearest track to you that I know of is the remote world track in Slough. It's actually a 1/8th buggy track that is used most Sundays for racing, although it's in a public park so lots of people (myself included) go use it on days other than Sunday. http://www.remoteworld.co.uk/