I’m from Scottish Borders so only a couple of hours away, been riding down that way for a “few” years. Past couple of years we have been basing ourselves in Skelwith Fold caravan park nr Ambleside which is another good base.
This http://www.golakes.co.uk/travel/New-Bike-Bus.aspx might help you get around ie based in the Windermere area you could get up to Keswick for the Borrowdale Bash or Skiddaw rides, Whinlatter if you fancy an easy day at a trail centre. 💡
http://www.theedgecycleworks.com/mtbroutes/skiddaw-circuit-and-summit/
Bike shops to visit for route info and possible lbs rides;
KMB, Keswick Mountain Bikes
Biketreks in Ambleside
Wheelbase in Staveley
postierich, justinbieber and a few others on here have good knowledge of Lakes routes