For some reason I wasn't emailed to say this thread had replies so I missed them. Sorry - I would have replied earlier.

The compression readings were taken by a local mechanic but they didn't have availability to do the repair until a few weeks. They are not my 'regular' mechanic anyway, I was just driving past when the EML came on so pulled in for a fault code read and it went from there. I took the car away and it is booked in with my regular garage.

A second garage confirmed it had low compression in that cylinder - its LPG converted and the I went back to the garage that did the conversion. It was a previous owner that had it done and the LPG installers remembered the car, they said the previous owner came back to them for a misfire and they found low compression on cyl 3. Thats as far as they went. The owner obviously sold the car on, and that person was the guy I bought it from. Private sale so no warranties.

I don't know what has happened since the fault began because it was obviously in existence when I bought the car. What I have done I have definitely exacerbated it but I drive my cars hard.

When I bought it, the misfire was undetectable - no EML, drove normally. It only appeared after 3 weeks of ownership and after I had thoroughly tested its performance for those 3 weeks.

It doesn't overheat but it does have a coolant leak from a lower rad hose. Its leaking only drips at a time but i guess if this leak existed prior, it could have caught a previous owner off guard and potentially it could have overheated in their ownership. This isn't confirmed though.

None of the mechanics think there is a problem with the block, they think its contained in the head, but who can say fro certain until they pull it apart.

Because its LPG converted, it has 2 fuel delivery systems and 2 sets of injectors - the regular petrol and the LPG, the fact it does the same exact thing on both systems means I can rule out injectors, fuel pump, filters, bad fuel etc.