Well I've sdeen it quoted as after 55 plate and after 06 plate so don't know which (if either).
If anyone has an older model, maybe look around for a vehicle engineering place locally. Instead of paying £3k+ for a new box, it may be possible to get the relevant part sorted for £800 - £1k. This is because the box problems are often caused by water getting in underneath and corroding a bearing on the gear selection mechanism. If this is the issue, this work can be done more cheaply than by buying a new box.