Thanks. Yesterday morning after the car had been standing for 24 hours, both batteries were at about 12v. It has been confirmed that the original battery was a Bosch battery so it seems both batteries are over 6 years old?This link may help . As far as I can see there is no need to re boot any of the ecu things.Note the main battery has to be turned on its side to facilitate removal. The auxiliary battery needs the post fastenings transferring. I’m inclined to think a good auto electrician could do this for you at home with either he or you supplying the batteries. He may surprise you and say you don’t need both changing🤔
Will you be videoing your efforts😁
If the seat is moved completely forward and then raised up, there is no issue changing the battery, but the aux battery needs to be removed. However National Tyres part of Halfords, told me that the seat needed to be removed and only a Jeep dealer could do that as cables needed to be disconnected.
At ETB around the corner the fitter did not even know where the battery was located or how to check it. I had to show him. The same fitter wanted to replace the AGM battery with a lead acid battery! This set off alarm bells whcih is another reason why I asked on here about battery chargiung or changing. Either way I now know a lot more about batteries than I did a week or so ago.