The film was shot almost entirely on location. There was no filming in the real Penrith; the locations used were in and around nearby Shap and Bampton, Cumbria. Monty's cottage, Crow Crag, is Sleddale Hall, near the Wet Sleddale Reservoir just outside Shap, although the lake that Crow Crag apparently overlooks is Haweswater Reservoir. The bridge where Withnail and Marwood go fishing with a shotgun is over the River Lowther. The telephone box in which Withnail calls his agent is beside Wideworth Farm Road in Bampton.
Sleddale Hall was offered for sale in January 2009 with a starting price of £145,000. Sebastian Hindley, who owns the Mardale Inn in Bampton, won the auction at a price of £265,000 but he failed to secure financing and the property was resold for an undisclosed sum to Tim Ellis, an architect from Kent, whose original bid failed at the auction.