Thanks for the replies guys.
So I popped open the bonnet, it seems to be cylinder 1 gone now. Previous cylinder was no.3 but it's running fine.
I swapped over the coil over pack (COP) to cylinder 4 and it has switched over to that and so forth. Spark plugs are fine, no corrosion.
Car has done 260,000kms so far, so I'm assuming they all must be failing around the same time unfortunately.
Guess I'll look on ebay to see how much they go for there instead of Burson's, Repco etc.

Cheers