Setup of new account before the phone line is 'connected'?

[#1]

A friend has a slightly unusual problem....
He currently has Virgin phone and cable broadband. The Virgin phone number was his old BT number rather than a Virgin specific number. He has decided to drop Virgin and switch back to BT and use plusnet for broadband. Since his number was originally a BT number he is able to keep that but BT being BT won't switch the number until Virgin stop the phone service.
He currently has the new BT line (with a 'temporary' number) and the Virgin line (with the number he is keeping) which should cease tonight/tomorrow. BT conveniently say that it could take anything up to 2 weeks to transfer the number over!
Is is possible to set up a plus net broadband account using the 'temporary' number and have things keep working when the phone number changes..... I sort of suspect that it would be asking for trouble but it might work since it will be attached to the same physical line at the exchange (I assume).
Are there any other suggestions he can use in the meantime till the phone line is 'properly' set up? He would be quite happy to dial in temporarily but that won't work without the account set up and you can't do that without a phone number....
Help my brain hurts!

[#2]

Hi there,
It *should* work if we set up the broadband on the temporary number, as the broadband will be assigned a circuit ID once live, which a standard number change shouldn't affect.
Incidentally there is no way a number port should require the cease of the Virgin line first, but that's academic now by the sounds of it.
If your friend doesn't want to risk the possible disconnection of broadband (however small the risk should be) we can set him up a dial account in the meantime if that would be preferable. This would need to be manual though as we don't officially offer them anymore.

[#3]

He can sign up for a free PlusNet dial up account here and then upgrade his account to broadband when the phone is sorted out.
Edit - was writing this as Mand posted.  The link used to the dial up sign up was provided by Jameseh here.

[#4]

Thanks Mand and Paul. I thought I had read about being able to set up the dial up account to use first but could I find any reference to it when I wanted to!
I will check with my friend which option he would prefer and go from there. At least I now have the correct information to hand 

[#5]

No worries.
Give us a shout if you need anything else.