Bournemouth is in UK telephone area code 01202, which is +44 1202 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.)
That depends on where in Somerset.
01934
UK area code 01749 covers Shepton Mallet in the county of Somerset.
01691
01931 is the telephone code for Shap, Westmorland (near Penrith in Cumbria).
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.
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.
01792 is the area code for Swansea
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.
UK telephone area codes were first assigned in 1958.
The (01749) area code is for Wells/Shepton Mallet, in Somerset. Local numbers have six digits.