Whilst I would never say no the North Yorshire, and without prejudice to any future commitment to organising, I was thinking that the following areas have some great biking roads and might not be as busy as Cornwall/South Wales.
Lincolnshire Wolds - not the prettiest part of the world but some cracking roads from Lincoln to the coast
Scottish Borders (the other side) - Kielder Forest, Bamburgh, Wooler and Melrose all have some incredible scenery
Northern Ireland - come on, who wouldn't want to follow the NW200 route? plus we could pick up some Bushmills!!!
Hadrians Wall - having walked it I reckon there's a cracking route to be had around the arse end of the Empire
Just random thoughts