From: "Trevor Dunkerley"
Sortestan - has defeated me so far the ending could be sta = stathir = farm,
but it is a bit far south for that. Stathir is largely Scotland/ Isle of
Man, Cumbria. Sortes or any variation of it I can't find.
Could it possibly be, depending on the geology, quite simply 'Sort stone'
A HIstory of English Field-Names by John Field in the 'Approaches to Local
History' series, Longman, 1993, ISBN 0582 08157 0 is a good reference on