To call Abkhazia from the UK, you should dial "00+995 44 +7 840, 940+Phone Number". 00 is the Exit Code (IDD) of the UK, and +995 44 +7 840, 940 is the Country Code (CC) of Abkhazia.
To make international call, dial: Exit Code of your country +Country Code of the country you are calling to + phone number you want to call.