Just a quick update...

Using the Homehub as the modem (WAN2 into BT homehub).

The Homehub hasn't dropped the connection once and on first connect, connected at a higher speed than the Draytek.

I'm a bit disappointed as I was led to believe Drayteks were bullet proof but I'll keep it for FTTH when it comes.

And another update!

Due to some NAT and minor firewall issues, I've put a modem in place of the homehub. It's the old openreach HG612 (plenty on ebay) and it's pretty much bomb-proof. If any of you have issues with the draytek modem, I'd recommend doing what I've done.