Hi, Colin-
Greetings from Virginia, USA, near Washington DC.

This is always a tricky task, because finding a reliable pattern in
the data is difficult, as you're finding out. When you isolate the
post code out of the mix, you may find another pattern from there.

Do you mind posting some examples? If the post code always appears at
the end of the address, you might use and IF statement with a MID that
looks for a space 4 or 5 characters from the end, and isolate the post
code that way. If you post examples, for privacy reasons I suggest
substituting fake data.

Another technique that you may be able to use: you can use ASCII
character codes to look for upper and lower cases. For instance, you
can find the lower case "L" in "Colin" with this formula:
=SEARCH(CHAR(108),"Colin",1)
Character 108 is the ASCII representation of lower case L. One place
to find ASCII codes is
http://www.neurophys.wisc.edu/www/comp/docs/ascii.html

Dave O