<<< but their website states that he needs to be connected to the internet to recieve emails etc. >>>
You *ALWAYS* need to be connected to the internet to receive emails, it is an internet-based service. However, you don't need to be connected with a particular ISP to retrieve emails, even if the mail server is with another ISP.
<<< So what should he do regarding signing up? >>>
It should be posible to sign up on Virgin's website starting from this page click here
Unlike "dialup", where you can sign up and be online with an ISP in a couple of minutes, ADSL broadband involves having the service enabled on the phone line by BT and you have to receive a pack from the ISP which will include an ADSL modem.
To connect to the service "wirelessly", the supplied modem (invariably a USB device) will have to be replaced with a combined "Wireless Router/ADSL Modem".