Being new to smart phones, I upgraded from a O2 pay and go account to O2 contract by going into the store. The staff were helpful and they copied my contacts from my old Nokia6210 to the Galaxy Ace using a little simcard copy device. He continued to "setup" the phone, not sure what this was but it took him about 2mins, which was followed by a demonstration of how to use the basic functions like calling, messaging, email and personalisation.
I opted for the minimum package of 200 mins + 250 O2 mins + Unlimited texts + 100MB data. I was sure the 550 mins call time would be plenty, Unlimited texts, awsome. But the data of 100MB sounded very tiny to me but I don't know how much data a smart phone needs. I will have to see.