I've managed to change it okay... for future reference, this is what you need to do:
Floor where the driver and passengers feet are must be removed (i.e. the bit that goes over the gear stick. This should just be a case of unscrewing/unbolting the bolts and lifting it out. Drivers seat should also be removed (4 bolts).
For me this was complicated because several of the screws refused to move easily, and the floor seemed to be glued down with some black mastic (which must have been in 1998 when the car was refurbished).
Note - its not enough to remove part of the floor and attempt to bend it - it must all be removed.
With the floor removed, you then get good access, and it is possible to slide the shaft in place. I removed one of the bushes, and put this on the shaft first, before pushing it in. It required a bit of force, wriggling, and the occassional hammer to get it all in.
Once in place, the linkage can be reconnected, and the floor replaced... adjustment of the clutch (using the adjustment rod) will then almost certainly be required - but this is easy to do.
Hope that helps someone...