Where in the UK is area code 0793?

A UK telephone number beginning with 0793 is a mobile phone, with 7 further digits to the full number. In international format, that's +44 793. The conventional way to write the number is either 0793x xxxxxx or +44 793x xxxxxx.

(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.)