Common reasons for driveshaft removal include split gaitors or, more commonly, worn/corroded reluctor rings.

The gaitor is arrowed blue, the reluctor rings are arrowed red.

Chock the front wheels and leave the handbrake ON.
Jack up the rear of the car, remove the wheels and place on axle stands at the front of the engine frame.

Slacken the drive-shaft hub bolts (a 13/16AF imperial socket fits nicely but a 21mm socket may also work).

Now you can release the handbrake.

Drain the gearbox oil.

Using an e16 socket, and securing with an 18mm ring spanner, remove the tie bars from the chassis tubes. Note, these are under tension so will 'ping' out once you have removed the nut.

Remove the lower shock absorber mount using a single E14 bolt. It should be on a captive nut, but if not, secure with a 16mm spanner.

Once the shock has been removed, the chassis will now fall under its own weight.
Pull the chassis tube 'out' to create extra space for you to pull the splined shaft out of the hub.
Be careful of the bleed nipple for the rear brake cylinder.

To separate the drive shaft from the gear box use a pry-bar to 'pull' the driveshaft out.

The drive shaft is now free.

To refit, a sharp 'push' along the drive shaft in the direction of the gearbox will click it back into place.