Ok, so I ordered the Eir sim which came 3 days later. Then I ordered the A21s from the VF website for 89 quid using the Eir sim as the number I wanted to switch over to vodafone, which came 3 or 4 days later (ordered on Thursday, came this morning/Monday)
I opened the phone and stuck my Virgin sim in (just happened to put it in slot number 2, whoah whoah) and I can confirm that the phone was unlocked with no funny business. No need for anything else. A21s for 89 quid, happy feckin days.