Well you've told us where you want to go but you've not told us how many people are going!
Talcomb is set in a converted 17th century water mill. It sleeps 4 and is available, for that week, for �299.
If there's only 2 of you, Elm Cottage (part of Gallery Mews Cottages) is in Thornthwaite (2� miles from Keswick). It's available that week for �250.
Those are among the cheaper options found by searching here:
http://www.golakes.co.uk/accommodation/lake-di strict-holiday-cottages.aspx
Chris