In reply to Doug: Though it's older, I'd recommend the earlier book in the New Naturalist series, The Lake District by Pearsall and Pennington. I wasn't as impressed by Ratcliffe's book; it referred too often to the earlier book and had an academic style of writing, which made it hard work to read.
Plus the earlier book can be bought much more cheaply than the latter, which is never a bad thing.
T.