Thanks everybody for hints on blue smoke. It does drink alot of water! So that's one possibility. Noticed this evening that it was not too bad going out at 7 deg but coming back at 4 deg....same problem. I am taking it in tomorrow to see what the local garage has to say. I know the turbo is probably out of date but i'm hoping that some sensor to do with the cold and choke equivalent in a diesel might be an inexpensive fix. Will let you know what they say. Meanwhile I'll follow some of the links that you have kindly posted.
Cheers for those.
PS Not low on power especially but I think it would cause an accident behind if I really put my foot down after sitting at lights.