Thanks chaps.

Fuel filter was changed maybe 3 years ago but done around 2k miles since. The fuel is pretty recent TBH.
As for plug gaps, pretty sure they're twin electrode jobs IIRC and not adjustable as far as I know but i'll have to check. They're Ford PP8 platinum plugs, std fit on Escos' I believe.

If anything i've typed is made up please put me right!