In reply to Lynsety:
Tour of Cairngorms is great, but it's hardly midway!
There are some lovely quiet road ride loops in the Borders, SW/S/SE of Peebles. Hilly country, but the ascents are gently graded compared to most of the Yorkshire Dales. Potentially go as far south as Newcastleton and Eskdalemuir. Tibbie Shiels used to be a nice place to stay (probably still is, just I've not been there for ages).
Rob F