Eric,
Accu Spark replied saying "the coil is to be used in conjunction
with the existing ballast resistor." All good I thought.
However, upon fitting, no start. I bypassed the resistor and it started.
I checked the resistance between the terminals [the primary winding] of the new
coil and it read 2.8ohms. I am uncertain whether the absence of the resistor could
damage any other part of the ignition system.
I'd have thought that a coil advertised as a 1.5ohm coil should produce a similar reading?
I'm sending it back.
Refitted the old one and all's back running.
This conundrum will wait until my return from France. She's running well enough for that.