This topic has been covered in great detail in other threads in this forum - most of them late last year when the device hit the shelves and the short answer is no it cant be done as the hardware has been found to lack the 850mhz radio.
In a few months it probably wont matter as Vodafone will switch on their new3G 900mhz network extension and i can bet you that 3 users will get access to it. It wont make sense for VHA to operate a national 3G network and only give half of its subscibers access to it whilst the other half roam on its competitors network. Just my opinion and what I would think would make good commercial sense and im sure these guys will be looking to get a return on their investment so I would wait and see what happens. Our touch pro works fine on 3G 900 as I have used it in Optus' 3G 900 zone.
HTC One X, One XL and One S, Galaxy S2