I was sent an email on the 27th October stating the following when I asked if I could change the plan I'd selected: (Highlighting is mine)

As for your order in particular; we are not able to amend any of the order details (to protect customers information). Normally we would have suggest for you to request a cancellation of the order and place the preferred order again on our site. However, we have now been told that we are not able to accept any more orders for the handset on T-Mobile; all outstanding orders are going to be fulfilled however it will not be possible for you to place an order again for the time being. We have not been told why this is, however it is likely to be something to do with our agreement with T-Mobile for supplying the handset. This is not the same for Vodafone as we are still able to supply the handset with this network.

So from that it would appear that they should be honouring all our orders. Then again my order should have shipped on 19th October.