Chalk.

I'm in Hampshire not a million miles from Salisbury. You have Wilton Garden Centre (good but expensive) and one at Netherhampton that are very close to the city (there may be others), you also have the Cattle Market over in Netherhampton where they hold sales of horticultural equipment and plants several times a year so if you want fruit trees or something large that's a good place to get a bit of a bargain but you will still pay a fair price. There's also a Tuesday and Thursday market that had a couple of plant stalls, a few things may have changed since I was last there but they are probably still trading there. There are lots of garden centres in Hampshire and Wiltshire, you're also not all that far from Somerset and Dorset if you have transport. You might like to try the RHS Nursery Finder to see what's close to where you will be living. Weather tends to be mild here for most of the year and the City is fairly sheltered. As for soil conditions I don't know, there is a lot of chalk land on the plains but Hampshire is also almost all chalk apart from the region where we live, it's acid so who knows!

Here is a link that might be useful: RHS Nursery Finder