Thanks for reply. Checked oil filler cap and dip stick - no milky residue, coolant in expansion tank was a bit low added about a liter but as there was no warning light, can't say if it had been at that level before problem started. gave it a quick start, it started with a bit of white smoke and then a few seconds later went away, certainly nothing like that experienced yesterday but still not smokeless as the day before that. Don't have the correct tools to extract the spark plugs so off to the shop it goes - will see what they say...