why not install a 40w thermostat oil filled rad (tube) under it and leave it on 24/7 let the stat do the work! It would all need to be installed in an enclosure.
Sector is an own brand CU from rexel senate electrical wholesalers.
The newer ones are rebranded electruim CUs, the same as wylex, volex, crabtree etc are.
IIRC the older ones were rebadged GE CUs
I saw a few fires, normally in a cloakroom with coats and other general clothing covering the board, so any poorly terminated cables got hot and there was all the combustable material to feed a fire, right there!!
A very long test lead, We use them for testing Gas and water bonding cables. He could also disconnect supply from off peak short out one end and test continuity. He just needs to check its the correct supply lead or “bang"
Why don’t you take the opportunity to replace the ballast transformer and lamp to mains operated GU10 LED lamps. No transformer to go wrong in the future and future proof your home for when they discontinue CCFL lamps
Why don’t you put a GU10 to test lead adapter in with some long leads or even a lead off the back of the lamp socket and see what the voltage is doing!