Where in the UK is area code 01702?

UK area code 01702 (or +44 1702 in international format) is for Southend-on-Sea, Essex.

The city Southend-on-Sea and its surrounding towns and villages including Canewdon, Eastwood, Great Wakering, Hadleigh, Hawkwell, Hullbridge, Leigh-on-Sea, Little Wakering, Marine, Rochford, Shoeburyness, Southchurch, Thorpe Bay and Westcliff-on-Sea.

(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.)