I apologise for my slow reply.
"Don't forget your passcode" Unfortunately my wife has no idea what it is, as one of the staff where she bought it did everything for her, and didn't communicate any useful information.
We were going to another mobile shop to ask them to test using another sim, however, we don't need to now. Last night the iPad came up with a message on its own, saying it had completed an upgrade. The GSM connection then started working of its own accord! This despite the Apple shop telling us it was broken and we needed to buy a new one.
I'm just so pleased that I joined up here to ask for info about IPads, as I just didn't feel what they told us in the shop stacked up. We won't be going to that shop again (Udon Thani, Thailand).
Thanks again to everyone who replied and offered advice.