Thanks for the idea but it didn't work. It looks like the BT website is knackered, I'll give it another go in the morning if it doesn't work then I'll place my order over the phone.
Yeah it's good cashback through quidco I'm planning on using it to buy a decent dual band router and ditch the HomeHub.
I kept getting same error so in end I used the agent chat window and she told me to use the "non working line" option and then you can enter your phone number later in the process and the order went through okay.
Install date now in 3 weeks time.
just got to work out now whether to lay ethernet cable to upstairs for my PC or use wireless usb/pci card. My wife uses a laptop so thats not a problem.

unless you have turned it off like 50 times ^^