Where in the UK is area code 01482?

UK area code 01582 (or +44 1582 in international format) is Luton and other surrounding communities including Dunstable and Harpenden.

(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.)