This is the start of my northern route from home, just gets better, as you leave Ambleside behind, and climb up over Dunmail Raise, past Thirlmere and up to Keswick. No wonder voted one of the 3 best driving routes in Europe, and currently I have to commute every day on it :)
would agree entirely, tourist season lasts most of the year incidentally, these days! Just choose wisely when and how you do this section, could end in tears all too easily.
Take the B5285/B5286 to Ambleside and back down the A591 to windermere. B5285/B5286 VERY tight and VERY blind, but good fun! Give the tourist season a miss though