As far as I know the Sony uses the standard method (well it works for me anyway) which is:
1. Unplug the box.
2. Hold down the backup button on the front panel.
3. Plug the box in and keep the button pressed until all 3 of the LEDS illuminate, you should get an onscreen message warning you that an update is in progress and that you shouldn't disconnect, power off, etc.
That should do the trick.
Incidentally when I called Sky earlier this week to pre-register for Sky Plus, they still didn't have a clue when the EPG planner updates for the Sony boxes would be available. They trotted out the old "We're doing them in batches and haven't got round to you yet" story, which sounds pretty unconvincing

.