So I figured I'd better update this thread for the future, now that I've sold the FL2.
I ended up doing the head gasket again.
The car had started to pressurise the coolant, and this was accompanied by a misfire, especially when using more than about 50% throttle when cold.
Because of the coolant pressurising, I stripped the head off for replacement, as the fault could only be head or gasket related.
As it turned out, the HG was the issue. It had failed between the centre cylinders, and there was staining between No1 cylinder and the adjacent coolant way.
This time I had the head re-faced, as there was some minor burning where the gasket had failed between the cylinders, I probably should have had it re-faced before I did the job last time too.
I also used a BG head set last time, which may have been a factor in its early demise, so this time I went genuine or OE for the part needed. Even the BG set bolts broke when trying to remove them, adding to the time it took to strip the engine down.
So avoid BG parts like the plague.
Here's a few pictures of the relevant parts of this post, as anything normal is already shown above.
View attachment 326315View attachment 326316View attachment 326317View attachment 326318
Hopefully the engine will now have a long and reliable life with the new owner.