+44 is the telephone country code for the UK. A number beginning with +44 78 is a UK mobile phone.
(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 Aberdeen, United Kingdom is 44, (0)1224.
Until the early 1990's, area code +44 21 (or 021 within the UK) was Birmingham, which is now area code +44 121 (or 0121 within the UK). There has never been an area code +44 217 (or 0217) in the UK.
Country code +44 is the UK, and +44 3 is an all-UK number.
Cambridge is in area code 01223, or +44 1223 from outside the UK.
Country code +44 is the UK, and +44 7926 is a mobile code, along with the rest of +44 74 through +44 79.
Country code +44 is the United Kingdom. Area code +44 1303 (or 01303 in UK domestic format) is Folkestone.
The Brighton, UK, area code is (01273), or +44 1273 in international format. Local numbers have six digits.
Witham, Essex, is in area code 01376, or +44 1376 from outside the UK.
Numbers beginning with +44 75 are mobiles in the UK.
Bodelwyddan, Wales, is in UK area code 01745, the same as Rhyl. From outside the UK, that's +44 1745.
Runcorn is 01928, which is +44 1928 internationally.
Holsworthy, Devon, UK