Finally got to the bottom of this one, both George and Kev pointed me in the right direction, engine was very noisy mechanically so took cam cover off and the inlet rocker shaft was loose,so much so that the valves could not be fully compressed on no. 1,hence the fluffy miss.

Next step was to physically check timing and inlet cam had jumped 4-5 teeth,my theory is that this caused piston to valve contact and it was that "hammering" effect that loosened the rocker shaft bolts via the rocker arms.Anyway,fitted new chain kit put it all back together and goes like a good un

My recovery guy had one last week which had done the same but his was a non start and on his all the rocker shaft threads were wrecked so needed another top half of head.