I never bother to put in a space when entering our UK postal code into any on-line website for any reason. I cannot recall a single occasion in the last 10 years when this has caused a problem.
For navigation, I almost invariably use the Post Code feature in my Tom Tom without entering a space, and it works fine every time.
(By the way, even the Royal Mail's UK address finder, from a UK Postal Code, does not require a space in the postal code entered as the search string.)