Sorry should have said the problem is Petrol or LPG exactly the same.
Cheers for all that info Steve I will email it over to the garage tonight so they can try it all in the morning, What you say is very logical.
"After the O2 sensors were replaced the car then drove OK for a short while then reverted back to misfiring, this could be another indication of a faulty ECU as those capacitors are affected by heat, could you leave the car to cool right down then restart and see if the engine behaves until warmed up?" Yes exactly as you say.
Can the new Oxygen sensors, be blown, was the term used so that they don't work anymore. ?
I left them taking the crud off some terminals that go to the ECU.
Have a great weekend everyone Mike.