The SM is mounted behind the engine block on the clutch/gearbox/flywheel side. To get access you have to remove the plastic air ducting - a big jubilee clip to undo, a plug to take out, and an air breather to slide off - and take off a cast-metal support which is bolted on between the engine side of the air manifold and the manifold itself - 4 x 12mm bolts. Once this bracket is out you can see the SM clearly. There is a steel support which comes across, which has to be undone at the top (13mm bolt I believe) and moved over: to be able to move that you also need to have slackened off the bolt at the other, bottom end of this bracket: I had to do this from underneath, so had to raise the car to do that. At this point make sure that you have the negative battery terminal disconnected (and make sure you know your radio code, or put a code-saver into the ciggy lighter socket). The SM is held by 2 bolts, one from each direction. Disconnect the 2 wires from the SM - there's the big fat one from the battery, and the thinner wire which comes from the "ignition/start" switch. Undo the SM bolts and then the SM can be manoeuvered upwards and lifted out. Fitting is the reverse procedure: but take care not to over-tighten the nuts on the SM wires as the threads are made of copper and very easily damaged!

So - the procedure is this:

Make sure your fob battery is good. then...

Put key in ignition and turn off/on 6 times within 10 seconds: this puts it into programming mode, and is acknowledged by the indicators flashing twice.

With key in the lock in "off" position, hold down the unlock button on the fob and press the lock button 3 times, then release the unlock button. If reprogramming has been successful, the indicators will flash once.

Finally, turn the ignition to "on", then back to "off", and the indicators will flash twice to indicate that you have left programming mode. Then test the fob to see if it operates the central locking system correctly.

Yes the procedure really works!