To prepare the car, the gearbox has to be lowered at the nearside end so that the end plate can be removed. After some significant help from Nodge, I decided to try by just removing the battery tray (to access the gearbox mounts), the selector cable (so that it didn't get crushed) and the lower tie bar (so that the assembly would drop as far as possible). The limiting factor is the inner driveshaft joint hitting the subframe as can be seen in the photos - but it can be done if you drop it as far as possible without damaging the inner joint boot.
Remove and tuck selector cable out of the way the other side of the subframe to prevent damage.
Remove the lower tie bar and bolts and put out of the way to allow the engine and box to tilt to one side when lowered.
When you are sure that the gearbox end is supported adequately (I used a transmission jack) then loosen and remove the 4 x gearbox mounts.
Lower, checking for anything going tight - cables etc - until the inner bootie says a very close hello to the subframe !
You then get a better view of the end plate and enough room to unbolt and remove it - see above in the thread for caution on the spring loaded nature of the plate - it comes off with a jolt once the sealant is broken. Gentle prising in the areas where the plate overlaps the box does the job.
Remove, clean (without getting sealant in the box!) I covered the workings with cloth while I did it.
Once inside the outer drum (the one required) just slides off. New drum in, align the notches in the clutches first and slide on, seal and replace end plate.
Don't forget the roller bearings - one each side of the assembly - they can fall off !!
Job done - once all that removed is reinstated and fluid replaced, level checked etc......
Now - let's go and look in the failed drum and take it into about 30 bits !!!