Oban is in UK area code 01631, which is +44 1631 in international format.
(The plus sign means "insert your international access prefix here." From a GSM mobile phone, you can enter the number in full international format, starting with the plus sign. The most common prefix is 00, but North America (USA, Canada, etc.) uses 011, Japan uses 010, Australia uses 0011, and many other countries use different prefixes.)
The country code and area code of Coventry, United Kingdom is 44, (0)24.
The country code and area code of Birmingham, United Kingdom is 44, (0)121.
The country code and area code of Cambridge, United Kingdom is 44, (0)1223.
The country code and area code of Scarborough, United Kingdom is 44, (0)1723.
The country code and area code of Northwich, United Kingdom is 44, (0)1606.
The country code and area code of Moscow, United Kingdom is 44, (0)1560.
The country code and area code of Hunstanton, United Kingdom is 44, (0)1485.
The country code and area code of Bicester, United Kingdom is 44, (0)1869.
The country code and area code of Barnstable, United Kingdom is 44, (0)1271.
The country code and area code of Basildon, United Kingdom is 44, (0)1268.
The country code and area code of Devizes, United Kingdom is 44, (0)1380.
The country code and area code of Workington, United Kingdom is 44, (0)1900.