Following my misdemeanour with my clutch slave cylinder replacement - thankyou those of you that offered help - the sad fact is that this apparently benign activity CAN result in splitting the gearbox / engine unit.
The post that the release arm sits on will come away from the bellhousing remarkably easily and cannot be put back without opening the bellhousing. I could not believe this either but it was confirmed by two of my local LR dealerships, it has happened in the past to each of them.
To reduce the chance of this happening, remove the two bolts from the slave cylinder to bellhousing and whilst supporting the body of the cylinder have someone put their foot slowly on the clutch pedal to eject the pushrod from the slave cylinder. Once you can get hold of the pushrod, slide the cylinder right off. The problem occurs if you simply pull the cylinder away from the bellhousing; because the dust cap "grips" the pushrod it effectively also pulls the release arm away from its pivot post, with the danger it actually comes off. At the very least, you risk detaching the pushrod from the release arm, not quite as disastrous but still to be avoided!!
Hopefully this will stop others from suffering the frustration that I have just experienced. One other note, if you are splitting the g'box from the engine for some other reason, consider modifying the pivot fixing into the bellhousing; I have now tapped an M4 grub screw into the side of the pivot pin to make it very difficult to come out in an unplanned manner.
Take care, Dave