Got some iridium plugs on the way. Ordered them from here, They seem to be a fair bit cheaper than everywhere else, I hope they're the real deal.The plugs I have have only done around 4000 miles, but they are around 2 years old. They've done a lot of cold starts and running on tick over on my drive as life gets in the way of me going out for a proper ride.As suggested I'll put all the mixture screws back to factory. I'll still try and clean up the current plugs as best I can and use them to see if the over fuelling issue is resolved before I put the new iridium plugs in and foul them up.
Still has a bit of a lumpy idle but I think I'll just live with it.