Firstly, thanks for your response and guidance. Very much appreciated. I’ve since replaced the battery (old one was shot after being laid up for 8 months), checked all fluids and all seems good (coolant was indeed only halfway up the tank!). Good enough to pass its MOT yesterday and she ticks over beautifully, so I’m happy.
The only thing remaining is the current draw, but I’ve also discovered whats causing that and yes - its the immobiliser. After pulling Fuse 7 the amp draw dropped from 0.25mA to 0.02mA. Not sure where to go with this now as I’m guessing its not going to be cost effective to sort out.
Is there a way around for the immobiliser? At the moment I’ve put a physical battery isolator switch on the positive terminal, which means I have to lock the car, unscrew the switch and then unlock the car with the key when i want to use it to put the isolator back in 🙂
Any ideas?