Its possible to validate your UK Postcodes using a regular expression.

Step-by-Step Instructions:

Step 1: Drag and drop an question node onto the canvas. Specify the type as “text”

Step 2: Under “Advanced Options” select “Regex”

Step 3: Copy and paste this regular expression:

([Gg][Ii][Rr] 0[Aa]{2})|((([A-Za-z][0-9]{1,2})|(([A-Za-z][A-Ha-hJ-Yj-y][0-9]{1,2})|(([A-Za-z][0-9][A-Za-z])|([A-Za-z][A-Ha-hJ-Yj-y][0-9][A-Za-z]?))))\s?[0-9][A-Za-z]{2})

Step 4: Under preview you can test by entering a UK post code

Step 5: To the right you will see either a red failure or green success icon under “Validation”