Thank you I will go and see where I can get one

All you need is the same ampage and wattage over hours and terminal side. I.e. The pos is on the left, then look for any battery on left.

I checked on AI and they confirm that the battery that I need to replace being the one I show in the image is a battery which manages the electrics for a hybrid vehicle which is why I get no response at all when I turn on the ignition as it only registers 5V on the meter. So it would seem I need to replace it with the same type S55D23R-B if I can find one!!

I am wondering whether yours is a post 04.2008 model as I can't locate anything similar to mine on Amayama. but then I'm not entirely sure where I am supposed to be looking - this is on the roof above the rear door isn't it? Wait - could it be this one?:

What is this battery used for? Is it an addon for the camper electrics? It says 'high performance AGM starting' (and CCA is 730 amps) but if it's just for your camper stuff then it may not need to be a 'starter' battery - another kind of leisure battery may suffice. I think the battery in the centre console is the one used to unlock the hybrid battery which then starts the car, and it sounds like that is all working. So if this is for your camper side of things, what kind of loads do you have (any hungry electric heating/cooking, inverter, etc)?

Heres my finished article. Two M6 screw bolt on the rear, there are 4 little screws to undo. Once undone you can thread the bolts through the rear mount. Then mark your hole positions on the dash just above the cupholder and drill using a 6mm drill bit. Wood or metal will be fine as it's thick plastic. Then screw the backplate onto the cup holders and push into the holes and nut up the bolts. You will need to remove the trim where the radio is but put the car in N, and the panel lifts up, carefully as you need to undo 5 wiring connectors. Then you've got a fully new cup setup.