I managed to turn it off this morning (with battery disconnected), so maybe it’s intermittent, or many there is a capacitor or something that stores charge which had run out. I lost 6 miles on the range overnight so it was using the other batteries to stay alive even though the 12v battery was disconnected.
Managed to get the relay out. That was a pain in the neck. Even if it worked before, I’ve cracked the plastic head so need to replace it anyway!!
Typically where I have cracked it is where some of the text is.
So it says on it that it’s a NAIS cm1a-r-12v-h91. Searching for that doesn’t help in terms of buying a new one, but does lead me to an image of the text I can’t read due to the cracks. Which is ACM33221 M44.
Searching for ACM33221 leads me to lots of relays I can buy, but they have different M numbers. Does that matter?
(Thanks for all the continued help by the way!)