Coverage

Coverage is the most important factor in choosing your provider frequently more important than cost. Each of the four networks claims to offer national coverage of 99% of the population, although each provider has "blackspots" without coverage, even inside major cities. The best way to ensure a provider has coverage where you need it the most is to try one out for a few days. If you are not satisfied with the coverage, most providers will allow you to cancel or switch to another provider as long as it is within 30 days.

Larger corporations with employees who travel frequently have historically used Vodaphone. That is primarily because Vodaphone and BT Cellnet primarily use 900 mHz networks, the same that most Continental European networks use. If you subscribe to Orange or One2One (which use 1800 mHz networks) and if you travel frequently, you should buy a dual-band phone. All providers have extensive network affiliates outside of the UK, although Vodaphone and Orange offer the best European coverage. Anyone who travels frequently to Asia should buy a dual-band phone. For travel to the US and Australia, you will need tri-band phone, although this will work only in major US cities as GSM coverage in the US (called PCS there) is still relatively spotty.