Rather than add this comment to an old deal, it is probably better here.
The Samsung U600 12 months free on Vodaphone form PhoneBox direct looked great, until the fact you could port your number across.
After several emails with Vodaphone I got the below reply...
Thanks for your email. I'm happy to hear that you're interested in opening a new Vodafone account. I have some information for you.
If you are currently with O2 there is no reason why you shouldn't be able to transfer your number when you buy your new phone.
Phonebox direct are a third party dealer and are capable of transferring your number for you. They can refuse to offer this service as a company. However I can't think of a reason why they would wish to do so.
I hope I will be able to welcome you as a new Vodafone customer soon.
If you need anything else ****** then please don't hesitate to contact me.
Vodafone Customer Services"
So looks like it is Phonebox direct who aren't moving the numbers for whatever reason (i did ask if it was to deal with any deal they had with vodaphone about bring fresh new customers in)...