Thanks for the answers i asked because on looking in the tank and having a sniff couldn't smell diesel .
I filled up at the station on the roundabout north of boxhill, i definitely filled up with unleaded albeit from the pump with a diesel nozzle.
(green premium unlead sticker on nozzle and on the place where it sits, diesel nozzle is black ) .
Tank was about a third full when i refilled , got about 5mls onto A29 when it started to hesitate on acceleration, i thought it may be carb icing so stopped to let the carbs warm up while doing this i was blipping the throttle and noticed bluey white smoke when i shut off .
Started off again and thought no more of it as it cleared up at the top end of the revs , by the time i got near home it was not accelerating properly and backfiring on part throttle, then it went onto 3 cylinders with clouds of bluey smoke on the overrun.
Got home but it wouldn't start next day i'm not convinced it's diesel because surely i wouldn't have got 40 odd miles from boxhill
And also if it was burning diesel surely there would have been smoke under acceleration
there was none why only on the overrun did it smoke ?? i was using the top end of the rev range because that was the only way to get any decent acceleration.