Our sim cards are with the Three UK network. The Three UK network covers 98% of the UK population (source: http://www.three.co.uk/discover/Awards/YouGov_most_reliable_network)
To check network coverage, please click here.
(The coverage map shows the scope of your coverage area. Map depicts an approximation of outdoor coverage. Actual coverage area may differ substantially from area shown on map, as coverage may be affected by terrain, weather, foliage, buildings and other construction, signal strength, customer equipment and other factors which do not allow Three to guarantee coverage or network availability.)
The Three UK network operates on the following frequencies:
3G: 2100MHz
4G/LTE: 800 MHz and 1800MHz
This means that almost all phones from Australia will be compatible on the Three UK network.
Specifically, all iPhones are compatible on the Three UK network.