Is it post code or postcode?
Future Perfect liaises with Royal Mail and Ofcom (as well as other such bodies) to ensure that its information is both accurate and regularly updated.
The Royal Mail uses this as one word, although it is clearly derived from ‘a code which directs the post’. We should, therefore, write this as ‘postcode’.
Incidentally, when writing addresses in block form, you should always try to put the postcode on a line on its own. If you have to write it on a line with another element (or you are writing the address in linear form), then it must be separated from that element by a comma (just as with any other two or more items which you separate with a comma).
Examples:
Future Perfect
52 Whitchurch Avenue
Broadstone
BH18 8LP
Future Perfect
52 Whitchurch Avenue
Broadstone, BH18 8LP
Future Perfect, 52 Whitchurch Avenue, Broadstone, BH18 8LP