COUNTRY PLAYBOOK ยท UNITED KINGDOM
Keep a UK mobile number active abroad.
The safest default is to preserve an active UK carrier-issued mobile number while you audit accounts, then compare PAYG, low-cost monthly, hosted mobile and VoIP routes separately.
If you want to keep the number, obtain and use the correct porting route while the service is active. Ofcom documents PAC-based mobile switching and a limited post-cancellation right, but provider recovery still needs direct confirmation.
Lowest-cost route
A UK PAYG or low-cost SIM may be the strongest value for bank and government messages, provided you can satisfy inactivity, roaming and activation rules. Record the exact minimum chargeable activity and set reminders well before the deadline.
When you cannot activate in the UK
Ask the destination provider to confirm overseas first activation, port completion and Wi-Fi calling setup in writing. A trusted person can help with a physical SIM, but never share credentials, recovery codes or live OTPs.
Hosted 07 and VoIP options
Hosted mobile services may preserve an 07 number in an app. VoIP and number-parking routes can be inexpensive for calls, but neither should be assumed to receive bank or government short codes. Verify number classification after porting and the right to port back out.
giffgaff as one example
giffgaff is one UK option, not the product focus. Its porting and long-term roaming terms must be checked against current official pages; an inexpensive plan is not automatically safe for indefinite overseas use.