A few observations which confirm much of what has already been said :-
A recent strip down ( yesterday) has shown the broken spring problem and when part of the spring finds its way out of the housing it can jam the clutch and prevent it from releasing. A broken spring left unattended can be disastrous for the flywheel and pressure plate when fragments of spring steel find their way in between. This one was examined and found to be good two weeks ago so I think the fracture was present (hair line) but undetectable - for this reason I would recommend a new or refurbished ( with new springs ) friction plate at every opportunity. I sell a refurbished friction plate for a bit under £100:00 a new flywheel/friction plate/pressure plate assembly will cost in the region of £1200:00 - it makes sense to replace.
I have heard that the slave cylinder can fail without signs of external leakage but suspect this to be tied in with spring failure.
Approximately 50% of the clutches I dismantle have broken springs!!!
If you have had a broken spring issue with part of the spring stopping clutch release then replace the slave cylinder as well because it will have been tipped at an angle by the obstacle and they are quite fragile. There are lots of makers of concentric slave cylinders ( CSC ). Not all genuine but all of the factory ones I have seen carry the Volvo mame + part number 8675052. They also carry the FTE logo +part number 6795. searches for either will come up with lots of makers with no idea of country of manufacture - buyer beware, as they say.
I would agree with Vitesse - there is not a lot of room for an external cylinder.
