Thanks heaps Phil & John
All the batteries are physically identical, but may not be chemically.
I think I'll do the nine 12v sets and charge each bank individually for safety's sake at the moment. When they eventually make it down to the property we'll decide if we go solar, wind, micro-hydro or a mix. My workshop car battery charger is a reasonably good one (read: not a SuperCheap special) so I'll see how it goes.
Wow - the fun starts - carrying them all
Thanks again!