Sounds like one or two things....
1 and the cheapest and easiest thing to check is the 30 amp fuse that operates the pump, has it blown?
2. lock the car up and don't worry about it... Seriously... sometimes the selespeed system can play up and then resolves itself after a few hours of settling but it is a sure sign that pressure loss is starting to happen.
3. Check the battery terminals of earthing points, selespeeds don't like dodgy earth connections!
4. You are loosing fluid pressure possibly from the the pressure accumulator (part of the selespeed actuator). The selespeed pump pressurises the fluid for the selespeed actuator to allow it to select gears & move the clutch.
If you are loosing selespeed fluid pressure, the pressure accumulator needs to be thoroughly checked.
Sorry but can't help you beyond that m8 as thats basically all I know abot selespeed issues.
Yessssss! Nero black, Black momo leather, sunroof and air con in a 156 2.0 twin spark..... = Heaven, pure heaven
Anyone can give advice on cars like "replace this part, replace that"... Start with the simplest solution and then work your way through it logically... Its a hell of a lot easier and cheaper!