With Orange it may not matter as much if you go over the limit though....as it is more of a fair usage policy....where as O2 just say 500Mb straight up?
Yep you are correct, if any Orange plans say unlimited, they are actually unlimited, also they are pretty lax on their FUP at the moment, although there is some work going on to address this.
Also Orange will prob be refreshing their plans in august properly and I expect the unlimited elements will go a similar way to O2.