In reply to Runtothehills:
Park near Stonethwaite in Borrowdale, walk SE with the river on your left until you get to a place marked Johnny House on the map, cross the river via the bridge, head back to Rosthwaite on the path, drink at the Scafell, then back to Stonethwaite. Flat all the way, a bit further than the Buttermere walk, and the pub's more than halfway round. Scenic and quiet.
In the same area, park just by the bend in the river on the small road that heads south off the main Rosthwaite-Seatoller road opposite the Mountain View cottages (£3), walk up to Seathwaite on the east side of the valley, and return along the quietish road (depending on the season) on the other side (or the way you came). Cafe at the farm, pub in Seatoller.