I found this uncredited painting on the excellent Shap community website http://126.96.36.199/~ruralweb/Shap%20Community%20Website.html. It appears to be a painting based upon the sketch which features on Page 48 of Burls 'Carnac to Callanish'.
The sketch is entitled 'The Shap Avenue. A sketch by Lady Lowther, 1775. From the south.