Another update.
D day is here. I'm still on Talktalk. just received an SMS from BT reminding me it will be "up to midnight" before the switchover.
Parcel tracking tells me my BT hub is ready for delivery at the local royal mail depot, so I expect that about 13.00 on past performance. That's fairly irrelevant, as I've more or less decided to keep using the Netgear, as it's all configured for my home network, and I know it works.
I had one more call from Talktalk which was strange, to say the least. They asked me to go through some security questions to make sure I was the account holder, but then before they did that they said "We see you've asked for a MAC". Yes. "Did you get it?" Yes. "Have you given it to your new provider?" Yes. "In that case I needn't trouble you any further". O.k.
Fingers crossed.
Cheers,
Axolotl