Hi Fionnula123,
Thank you for reaching out to us here on the Community.
I am very sorry to hear you are experiencing issues with your service whilst abroad.
Can you please check the following settings on your handset?
For Android:
Select Apps from the Home Screen
Select Virgin SIM Toolkit Icon
Select Roaming
Select Mode
Select Manual
Select International-you are done, go back to Home Screen
To Switch back when in the UK:
Select Apps from Home screen
Select Virgin SIM Toolkit Icon
Select Roaming
Select Mode
Select Automatic and go back to Home Screen
Thanks,
Nat