Simon Graham
You don’t mention how smoothly the car runs on start-up, but white smoke often means a failed glow plug, with that cylinder not firing properly, but improving with warm-up. Or alternatively it might be water in the fuel, probably from a failed head gasket. In reverse order to the above, unscrew the oil filler cap and look for any white “mayonnaise” of oil and water that could result from a cylinder head leak, and unscrew the cap (when engine cold) and look in the coolant header tank for any traces of oil. A cylinder compression check would give further evidence on this, but you’ll really need a garage electrician to check the glow plugs out. Otherwise, it could be worn/dirty injector problems, giving a poor spray pattern and unburnt fuel, but check the first two suggestions before you explore the others. I would appreciate hearing how you get on with these suggestions.
DCB Autos on Lynx Trading Estate, Yeovil get consistently excellent customer reports. I would try them first. Heritage Skoda in Yeovil are also well spoken of, but being a Skoda franchise will be more costly, if maybe better equipped. Hope that I’ve been of some assistance.
Doc Diesel