+44 70 (or 070xx in UK domestic format) is a personal "follow-me" number that can be forwarded to anywhere in the world. Be aware that they are very popular with scammers.
(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.)
This isn't a UK city code. UK city codes all start with 01 or 02
Australia uses country code +61, dialled as 0061 from the UK.
A UK number starting with "70" (or 070 when dialing within the country) is known as a "personal number". It is a number an individual or company can buy and then redirect to whichever phones they choose as and when they wish. For this reason they are popular for scammers and quite expensive, although they do have genuine uses too.
No one uses that code to dial the UK, which is country code +44, not +55. '00' is a commonly used international access prefix, and +55 is the country code for Brazil.
Watford
The area code "029" is assigned to the city Cardiff in Wales, UK.
Slough. There is no 0753 code in the UK.
The code 430 is not in use in the UK
York UK Branch
.UK is the Internet top-level domain for the United Kingdom, which includes England, Scotland, Wales, and Northern Ireland. In most cases, the Internet domain is the same as the ISO code used for things like currencies, but the UK is an exception. For purposes other than the Internet, the UK uses ISO code GB, as in the currency code GBP.
The country code for Poland is +48, and Kraków is city code 12. From the UK, dial 00 48 12.
Welwyn Garden City is in UK area code 01707, which is +44 1707 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.)