Hello Sonia, and welcome to the forum. We're mostly quite mad, but friendly with it
This is a good time to plant just about any tree, as it's lost its leaves (so doesn't need much water) and the soil is still (just) warm enough to allow the fine roots to grow. (Earlier in November would have been ideal, if you're doing it again).
They'll either be in pots (in which case they can be planted at any time), bare-rooted (dug up and most of the soil removed from the roots - can be sent through the post and must be planted in winter when they're dormant) or (possibly) with the rootball held together by a fine mesh bag (which has to be removed, also in winter).
No idea about suppliers, but someone who has will be along in a few minutes. You might try an internet search for fruit tree suppliers in your area.
Peach Avalon Pride is available from Reads Nursery http://www.readsnursery.co.uk/peach-avalon-pride/ . I've bought several fruit trees/bushes from them and am very pleased indeed with their service and the quality of their plants. They send very well-packaged plants all over the UK. You can email them for advice - they are very helpful.
I have no connection with them other than as a satisfied customer.
There you go. Dove usually has the answer!