Fireside Bookshop in Windemere has a few books about fell running.
Prices are twice the real value so best bet would be to negotiate much lower prices by telephone or visit the shop.
e.g.
Wild Trails to Far Horizons (£40.00 worth £20.00)
The Long Hard Road (paperback, two volumes £100.00, worth £50.00)
Running High (£35.00 worth £20.00)
Across Scotland on Foot (£9.50 available new for £5.95 from the Publisher Grey Stone Books)