I don’t know whether the hydraulic fluid in the lines is stopping me pushing it shut or if it’s something else. Genuine Saab plastic connector fitted between the clutch pipe and slave cylinder, also connects to reservoir feed pipe. Ah, yes requires "some force" to push all those metal fingers back can't quite remember think I jammed the big part against the car(Not plastic clip?

The Fiat "Quick Release" connector for the clutch line suffers a classic example of disimilar meta corrosion. You can you tube how to release the connector bit after years of salt grit etc it could be almost impossible to separate? Take the brass nut from the bulkhead end with you to get the correct thread and take the slave cylinder with you also.

For some reason the casing has cracked rendering theclutch inoperative and it seems I will need to replace the second part of the pipe onto which this coupling is bonded.

The 7/16 UNF 20 it exactly what I was expecting as its the typical Triumph/Land Rover Girling fair I'm use to, and they're nearly always 7/16 UNF 20. The aluminium corrodes against the stainless and the considerable expansion of aluminium oxide = a ruined fitting that will never separate. replacing both with new will be far easier than trying to separate the connection even though it "should" be a simple task of pushing in the plastic release part, but then nothing on the Fiat is that easy where rusting/corrosion is? Extruded Teflon tube with stainless steel single wire braid cover (1/8" bore) commonly used for braking systems.

We can supply a huge selection of Saab parts, including genuine Saab parts, aftermarket parts and performance parts. You've probably no chance, I didn't even try I just replaced slave and master so everything was new.