Thanks for the injector wiring info GW
Well it took some ingenuity to get the front plug out
both plugs were a bit sooty (may be due to low rpms urban commute?) and gapped OK, they were fitted 5k miles/2.5 years ago.
Tested coils, both OK so fitted new plugs and of course it ran fine, I hate not finding a definite fault as the next time I might not be at home when it fails.
Just got to adjust the clutch and put the bodywork back on.