Check the coil lead is on properly and in good order, also the electrical plugs to the coil.

Check all the connectors to the lump and ECU to make sure something hasn't worked loose or got damp into it. Start there but I am sure someone may have a less vague idea of wht it could be.

How did you check for a spark, spark plug out etc??

From the sounds of it it may need a good service, plugs and leads etc etc as the damp weather starts to play havoc.