Thought I'd post this despite having found the solution as it may help others save time.
Problem was soft top very slow to open/close and needed manual assistance (ie help from inside) to open it.
Hydraulic oil level was OK - and I lubricated the various pivot and folding points in the frame.

Turned out problem was the brass slotted screw in the motor/pump assembly used for manually opening/closing roof if motor/pump fails was not turned fully to 'close'. It must have worked loose over the years. An 1/8 turn or so to fully close the screw and it works like a good 'un.

Hydraulic fluid pressure must have been partially escaping through the valve that that screw opens.