9900 temptation.

Ola people,

I am extremely tempted with joining the BlackBerry family with the gorgeous 9900 but i have one problem.. My contract doesn't end for another year but my mothers is up in feb, and she has a free upgrade which she has given me due to being a techno leper. She is on Vodafone and im on orange, Ive owned Voda before and even as a PAYG handset they didn't seem to lock the phone to its network, but ive seen videos about needing a MEP code to do this on a 9900.. Will i need to buy an MEP to use my sim in the voda 9900 or will they not lock it?

Any ideas/ help would be awesome,

Cheers.