Bit of an update ...
Battery dead. I was going to go the boot route, but the boot would not open, so Plan B., the engine area.
The manual says to take off two panels which is quite easy, and the larger fuse panel, to reach a small upright + terminal.
It also says to use a negative area on the other side of the engine bay.
Interestingly, my portable charger cables were not long enough. So we extended it using a spare jump lead.
Tried twice to start it but no joy. Almost, but not quite...
Plan C - called the AA.
He tried twice and then it fired.
( He said it was his 4th Lexus dead battery call that day, and that we should run it for 20 mins., every other day.
He started it using the same + upright terminal, on the RHS, and the negative I assume, almost next to it. Not sure how safe that is?
Not sure if the small battery is ok, too small, all fine, a design fault, very cold, not used enough ...?