OK, I'm a dumb ass
I replaced my battery and for some unknown reason, I reversed the red and black. There was a spark when I started to connect the black and I immediately realised I had it backwards.
Connected it correctly, car started fin and everything appeared to be working correctly
Hadn't driven the car much since the battery change and when I started it last night, I got a battery/alternator light. Did a quick check via OBD and it is reading 10 volts running
I am guessing I fried the voltage regulator and/or the alternator.
Any thoughts?