Chas, do a quick sanity-check of the main items :
Starter cranking engine => starter OK
Headlights still shine (although less-brightly) when cranking => battery OK
Smell of fuel from exhausts after lots of cranking => fuel supply OK
As Stradale says, it's most likely the ignition electrics. If the ignition dash-lights are on then you've got power, & the problem should be with the coils, distributors, leads or plugs. Try a good drying-out with a hair-dryer, & if you can get the distrib caps off & dry in there then that could help. Note that the "WD40-type" sprays will tend to attract dirt & moisture later on after "drying out", so it's not a great idea to spray the stuff everywhere unless it's necessary. Try to clean-off any surplus afterwards.
Hope this helps a little.