cheers for the advice, timing should be fine (was done at BTM) and i've not had the problem before now which I thought i would have come across. What I did find is some melted red plastic stuck to the manifold and heat shield so my theory is during the MOT over the weekend the tester has left something, maybe an inspection light or whatever, near on on the manifold and its caught fire and melted the lid and bits of itself to the manifold.