Thanks for your responses. My iPhone is still locked to O2 in UK but I'm outside contract now so I could unlock it to use Q or V. I'm going to change my UK sim to PAYG just to use when visiting home.
For iPad, I've not bought just yet but I think I might not get enough use out of 3G when at home in Doha, (since I'll have the phone) and if abroad the roaming 3G is way too expensive, so I might stick with wifi only!
Decisions!!!!
Thanks again.