Preston, Lancashire, England, is in UK area code 01772, which becomes +44 1772 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 Preston, United Kingdom is 44, (0)1772.
All UK area codes begin with a 0. There is no area code 6010 in the UK, and there is no 06010 code either.
UK area code 020 is London.
There is no area code 20 in the UK
There is no 01134 code in the UK.
The country code and area code of Aberdeen, United Kingdom is 44, (0)1224.
017724 is too long for telephone code in the UK, 01772 is the code for Preston, Lancashire.
Cambridge is in area code 01223, or +44 1223 from outside the UK.
In the UK, 0121 is the area code for Birmingham.
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.
The area code "029" is assigned to the city Cardiff in Wales, UK.
Slough. There is no 0753 code in the UK.