you dont need dumps, the built in valves on the centre blocks do that job. Also will have built in check valves. (it is the built in nature of these that limit the flow handling and so the ultimate speed you will get)
you'll need four slow downs (i can see one on a middle pump) to balance everything up.
Looks like the racks will take 3 batts per side ?............. I would aim at 24v all the same at least to start with, it can always be changed to 36 easily later on.
Are you going to source sols, switches etc in UK ? You need to decide that before we can advise on what you should get and how a switch box will be wired (it can be done with simple 3 pin UK switches but will need diodes as well to get all the moves).
If you want I will design the circuits (oil and elec) for you but need to know where the bits will come from as US/UK will make things different. You will get the same moves/speed either way (switch box to include panic with UK switches will be more complicated but not a problem).
Big advantage of UK bits is obviously availability of replacements.................
It will be good to see a a bit of history back again. Jon will have given you a good basis to work on
