Blimey - I'd be impressed with people running PB's at Windermere. I spent a week round there one xmas and ran part of the course most days. Its not what I'd have thought of a PB course - very undulating. I reckon those PBers are just VERY good and 'hard' runners !
My PB course is actually London - 3.13. Thats from Green Start so not as crowded. Only thing is that often its the first hot weekend of the year - so that takes its toll sometimes.
I'm entering Edinburgh next year - that could be hot or cold - who knows - its Scotland ! And doing Leicester this weekend - so will let you know what I think of that.