Sounds like a damp/cold environment. WD40 does the job. But also weak/bad HT leads, pitted points etc. Recently I have had Coil failures on my TR +4. Replacement stuff is not what it used to be.
Button
I would agree with Button, the replacement parts are poorly made especially Lucas stuff in the green and white boxes. Try to by either NOS in the old red boxes or try someone like the Distributor Doctor for ignition parts / advice.
