So new battery arrived yesterday, gave it a charge overnight and fitted it this morning. Also checked all the cables to and from battery to make sure everything was good.
Let's just say it made a difference straight away, doing the window resets the windows went up and down the best they ever have, the dash lights look brighter and it seemed to start better. I have also removed all the non standard wiring and the headrest screens, yet another bodge job but slightly better bodge than the towbar electrics, no scotch lock connectors
Got two replacement headrests on the way.
Will now need to wait for a few days.