really? that means what we use in HK can be used in Northern Ireland and England? ...
It also depends on the sim card. For 3 (THREE network) sim, it is for smart phones only and cannot be used in other mobiles. But for other sim cards, most mobiles from HK can be used.
However, if you buy a new mobile in the UK, it may be locked to a certain network and will not accept sims from other networks. So you must check carefully before you buy a new mobile in the UK.