Think you may be onto something there, when i pulled the HT leads off the plugs, I noticed that the second plug was covered in white stuff! When I pulled the plug out, the plug was quite black and wet but then I decided to pull them all out and they where all the same.
Had a thought that it could be something to do with the injectors (now this I found interesting) so from left to right, I dissconected the plugs to the injectors, one by one and one at a time, whilst the engine was running. The 'lumpy idle' became worse when pulling the first 3 plugs, however, when i pulled the forth, the idle didn't change at all! So, lead me to think that maybe the forth injector was blocked maybe (electric plugs are all ok as tested with multi-meter)
So, pulled the fuel rail off displaying the injectors and cranked the engine over and petrol was sprayed out of all 4 injectors as it should. I was fully expecting the forth injector to not spray, or the spray to be distorted, but it appeared to be fine. This cant be normal surely?