As part of Greater London, Walthamstow is in UK telephone area code 020, which is +44 20 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.)
01931 is the telephone code for Shap, Westmorland (near Penrith in Cumbria).
01691
UK telephone area code 0161 is Manchester, but 0161 553 is an invalid number block.
UK telephone area code 01954 (or +44 1954 in international format) is Madingley, Willingham, near Cambridge.
A UK telephone number beginning with +44 754 is a mobile.
01792 is the area code for Swansea
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.
In the UK, area code 020 is London, but there are no numbers beginning with 020 2. Other countries may have similar telephone area codes.
There is no area code 0208 in the UK. The area code for London is just 020, with 8-digit local numbers. A number beginning with 020 8749 is most likely a BT landline in Shepherds Bush, but with number portability any specific 020 number could be located anywhere in London, served by any local phone company.
UK telephone area codes were first assigned in 1958.
Walthamstow East - UK Parliament constituency - was created in 1918.
Walthamstow East - UK Parliament constituency - ended in 1974.