Well after a weekends investigation, I reckon it was a corroded spade conector to starter. Took the downpipe off to have a look see, not a lot of space, to get it out you have to undo gearbox dogbone mount, so as to swing engine and give you space to retract downpipe, total bugger to do. Anyway once that was done, there is a wee heat shield over starter held on by three 13mm bolts, with this off I could see starter connection and the small spade looked rusted, cleaned it with sand paper and then reassembled whole lot. Car has been fine since, fingers crossed, but getting the manifold to downpipe to seal took four attempts. The springs used on the studs are unbelievable strong and its really, really bloody difficult to get both nuts on with the springs. First two times it was blowing when reassembled, I never replaced the cone so I guess I only have myself to blame. However third attempt with a bit of exhaust paste and it seems to be cool, although it aint faced a thrash yet. Starter hasnt played up since, so good chance I sorted it, time will tell. Dont recommend ever taking downpipe off unless you can really avoid it.
