00 is the UK's international dialing prefix, so 0039 is how you dial Italy's country code +39 from the UK. However, there are no valid numbers beginning with +39 4, so 00 39 41 is an invalid code as dialed from the UK.
Italy is an exception to the usual rule for most countries that you drop the trunk prefix 0 from the beginning of the domestic number in international format. All geographic landline area codes in Italy keep the trunk prefix 0 in international format. Thus, Italian area code 041 for Venice becomes +39 041 (dialed from the UK as 00 39 041) instead of +39 41.
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.
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.
There is no UK area code like 0491. If the number is pre-1995 then this area code is now 01491 which covers Henley-on-Thames.
UK area code 0161 is Manchester. 0161 644 is an unused prefix.