So managed to get a replacement Lambda sensor and get it swapped out after work. Found it to be burnt through from coming into contact with the exhaust 🤦
From the twist in the cables it would appear the previous one had been fitted whilst already plugged in so maybe that contributed🤷
Hopefully that should be an end to this saga and I can have a bit more confidence of not getting stranded 🤞
Managed to get the codes read and there was a stored code of P0135, specifying the heater circuit of the pre-cat lambda sensor. Live data showed it static at 0.475v
After watching this on YT the part from 15 mins suggest the sensor is caput, checked the wiring and there is no damage to short on the exhaust manifold.
Replacement ordered and will be a job for this evening/Sunday and hopefully this will resolve the intermitent issues.
I am going to see if there is a local auto electrician that can possobly read the ecu for any stored codes. I have in the intervening period where the car has been running fine had the boot loom checked and repaired so there are no breaks there that could be causing this.
OK so no nearer to the cause but have the car running again
The previous owner had fitted a battery isolator so something in my mind made me try using that to turn the power off, replace the fuse, put key and turn to position 2 then restore power. Fuse doesn't blow, usual immobiliser beeps, press unlock on fob to disarm and turn for ignition and the car starts instantly
¯\_(ツ)_/¯
Drives home flawlessly. I am developing a love/hate relationship with this car!