Dear Ian,
Only just seen your issues with replacing the water pump.
We have a 2006 365 GL and the water pump failed back in 2020. I fitted a new pump, but got irritated with the continuous stop start of the pump during operation.
I took advice from a friend who immediately said that I needed to fit an accumulator tank which is what Jabsco has also advised!
I fitted a Jabsco 2 litre accumulator tank and have been very pleased with it. Smooth water out of each tap and pump only clicks in occasionally as tank empties.
I managed to make a wooden cradle to hold the 2 litre Jabsco accumulator tank bought from F4 with the appropriate fitting kit. It does fit in horizontally in the std locker where the pump is located. Plumbing it in was relatively straight forward, only requiring cutting into the pump discharge pipe.
If you are interested, then message me back and I can take a photo of my installation when I am next on board.
Chris