The engine normally runs about 800 rpm. Recently this has increased to 1050 rpm. Put car into garage under warranty, Arnold Clark, Linwood. Their diagnosis is that the battery was low on power, and the engine rpm was compensating for the battery. Surely this means the charging system is not sufficiently substantive to charge the battery, while using auto lighting, air condition etc. Any one else found this problem.

Update from Feb 8, 2016: After the battery was fully charged, and I switched off auto lighting, the engine revs returned to 850rpm. Still seems the charging system is not substantive enough for winter motoring.