Following all the advice above, I managed to locate, remove and clean my
valve. The punch was perfect for getting it to rotate and help to work it free.
Thank you all for your input, saved me ££££'s.
I have been getting random "check injector" warnings and other times, engine suddenly losing power. I would have to pull over, stop the engine and restart. This normally resolved it.
I will keep you informed on progress. The annoying thing is if this resolves the problem, I have just bought a new car as wasn't confident in the Laguna anymore
Oh well, will feel better about selling it on if it is all working A1...