Recap:The car has been hard to start after running on LPG, for some time now (although it starts on petrol).
On a return trip from southern Italy three weeks ago, the car developed a severe misfire and engine knock on both petrol and LPG. Mechanic found oil in plug wells and replaced camshaft gaskets, after which it ran much, much better.
In the last two weeks, LPG has been getting progressively worse and generating lots of codes (misfire consistently on 302 and 306 as well as various lambda sensor errors), following which I've been running only on petrol and no codes for three days, until today. 430 and 420 which is the pre-cat issue.
At the moment, it runs perfectly on petrol, no misfire, no hard starting.
As I'm working constant 12 hour shifts, I haven't had time to locate and identify the LPG ECU, but I suspect it's OMV Dream XXI as per the injectors.