In reply to Dauphin:
If you're going for seven whole days, then surely it'd be worth getting up to the Cairngorms? It's not that difficult on the train. Start in Aviemore, and head down through Glen Feshie, and around the southern side of the mountains, up to Corrour then Ben Macdui, Loch Avon, and the Rothiemurchus Forest? Got to be better than the south downs way!