The Vodafone validation page will still send you a verification text message if your Facebook account is accepted, even if your current network isn't vodafone. It will fail at the next step and not actually activate the offer, but it is a way to check that your Facebook profile is acceptable before ordering a SIM (and once you have the Vodafone thing you have to go through the verification thing again, and that time it will complete to the end).
Looks like you're not a Vodafone Customer?
That's no problem! Bring your student card to one of our retail stores to get signed up!