Thanks, I'll take a look at the alternator for anything obvious.
On a side note I did check the wiring around the ECU for any issues and found a small green wire with a red stripe that has broken. Looks to have been like it for some time as the copper wire inside was all dark and no longer shiny. Trying to waggle the wire with the ignition on, the fault does not appear so.. a little unsure what this wire could be at this point.
https://ibb.co/Wn89KRS