Nitro® gurgled happily, sounding much like they
were saying:

Now I know why it is playing up, it can't be replaced as the torx screw
holding it in is completely stripped, no doubt it needed replacement
some time ago; but the old owner stripped the thread and never changed
it as the screw can't be removed.

The torx head is female and the centre is completely rounded, no room
for a dremel to create a slot, so how do I get the bugger out? Looks
like a garage job and money I can ill afford.

How big's the screw? If it's more than a fairly narrow thread, a LH drill
bit is probably easiest.

Alternatively, drill the head off it, so you can remove the coil pack.
Will that leave enough of a protruding stub to get a pair of mole grips
on?