Update: Leak has now been fixed - turned out to be a leaking hose from where it is crimped to the connector rather than the ram.
The vauxhall rams were not identical, just similar. Obviously made by the same manufacturer but there wasn't a straight replacement for the the longer ram that extends up towards the top of the roof which was the one I needed. The shorter rams are more alike and might work as replacements, but these are harder to get to on the Maserati and I haven't investigated carefully. The hoses however were the same - and the lengths matched the Maserati's.
Having a complete hydraulic system to take apart and see what would be involved in replacing a pipe was extremely useful and gave me the confidence to tackle the Maserati. A £100 was less than the cost of a single new hose so buying the Vauxhall unit still proved worthwhile.
Finding the source of the leak proved tricky because you can't observe what is going on while operating the roof - you can only see the before and after effects. The best I could do is isolate the leak to the top of the cylinder where it joins to the roof chassis (rather than the base where it joins the main body of the car). Having a spare hose enabled me to test whether the leak was from the hose or from where the hose connects into the cylinder. If it was the cylinder then it would have been a specialist job to replace the seal because you simply cannot get to it.
Replacing the hose cured the leak - a bit fiddly around the pump, but not too bad. The diagram on Eurospares shows you where each pair of hoses connects to the pump - disconnecting both from the pump and blowing down each pipe enables you to identify which of each pair goes where.
Forget about removing the old pipe - that would be a huge job - just thread the new one around the existing bundle following the same path and attach with cable ties. Cut the ends off the old pip as far back as you can to tidy up the loose ends.
So that's it - job done. If anyone has any questions about this they can PM me and I'll be happy to give any advice I can.
Thanks to all that participated in this small venture.
Mario