Selespeed query - yes, I have researched this to the max!

David, that was checked when it had it's service and was reported back as being right on the money.

All my leakage has been external as the underneath of the car and my drive can testify.

Another update... The car went in the day before yesterday to have the back plate on the actuator changed. The leak has been confirmed as coming from the weep hole circled in the picture.
Roberts Aerospace have never seen one leaking from here before so it's unique in that respect. Anyway, as 2 of the torx screws were knackered the back plate didn't get changed out. We've tried some very hi-tech sealant which sadly has only reduced the leakage.
The next step is to remove the actuator, drill out these screws & effect the backplate change.
On the positive side, other than this, the actuator gets a clean bill of health, has no mechanical/sensor faults, changes gear nicely and still gets me about.
A further update when I have it. Oh for the day when I can check the cs weekly

Well at least it's only 20 minutes to get the actuator off of those, LOL hi tech aero grade sealant, do you mean Silicoset? If it's not sandwiched into the joint then that stuff is like tits-on-fish.

Finally... 3 months on and the leak is fixed. It would appear that there are 2 ports inside the end plate that operate something vertically in the gearbox depending on which gear is selected. I suspect that the weep hole that the oil was coming out of is there to allow air in & out of the end space where the top seal of the arm sits and stop a vacuum being pulled. The top seal for this arm was passing and the weep hole allowed this oil out. Roberts Aerospace fitted a spare end plate that they had and so far it's used no oil over the last 2 days.

Now to find the cure for the flashing 3rd & 5th indication!

my 156 sele was flashing occasionally on 3rd and 5th, this was only a minor niggle, then it all went horribly wrong and the car spent a year in the garage after i couldn't get 2nd, this turned out to be the syncro in the gearbox, we reconditioned that then put it all back together and couldn't get 3rd or 5th, this was solved by replacing the selespeed ecu for £60 off ebay, had the car back for 3 days and it drives like a dream with no flashing.