you could avoid any risks of the unlocking not working or the phone not having the right bands by buying a cheap pay as you go phone from any of the phone shops, e.g.
http://www.o2online.ie/o2/shop/phone...ung-e1180/183/. vodafone and meteor also do similar deals.
then get a top up card for it, you can buy these in any supermarket or gas station or newsagent.
less technologically funky, but guaranteed to work 100%