What I was advised to do was save all my phone number to Phone on my mobile...so when I changed to my Greek sim card all i had to do was put 003 in front of the phone number and let my family know my Greek number to contact me. When you go home do the reverse.
If you use your UK mobiles (sim card) you will be charged at international rate and can be costly.
Go to Acharavi there's a shop that does mobile phone it open last year they are very helpful. Whereas before that, you had to travel into Corfu Town.