To call Kosovo from the UK, you should dial "00+377 44 / 45 +386 43 / 49 +381 28 / 29 / 38 / 39+Phone Number". 00 is the Exit Code (IDD) of the UK, and +377 44 / 45 +386 43 / 49 +381 28 / 29 / 38 / 39 is the Country Code (CC) of Kosovo.
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.