Thank you aussiblue. I confirm the variable camshaft oil control solenoids were the ones that had oil in the groove at the top of their threads and appeared to have sprayed some oil on the underneath of the removable engine cover.
The DTC code was P0302 and the cylinder that had stopped working was the second one from the left when looking at the engine from the front of the car (I assumed cylinder 2, but thought I would clarify in case I was incorrect). I am unsure if the DTC was because I had unplugged the coils when testing or if from the actual issue and was unable to generate it again after clearing.
I will see if I can find a borescope and have a look when I head back on the weekend.
Looking at the post from the link, the oil that was present in my engine was only a small amount and had not sprayed anywhere else in the engine bay, but what was there definitely appeared to be from the solenoids. It is possible that there is oil in the connectors on top of the solenoids so will check this as well.
I will bring the car back to the city on a trailer and get a compression test done.
This is a very rookie question, is the cylinder not firing because the
ECU has turned it off, given that the coil and spark plug appeared to work ok in a different cylinder? I figured that even with a compression issue that it would still generate some force when the fuel ignited, but in this case it appears that there is no activity in the cylinder at all which I find confusing.