Becca
the reason that cab were told to send the mail to wolverhampton is because all mail goes there first. Even if I address mail to the local pension service office in motherwell it gets sent first to wolverhampton who then check its not a bomb or contains harmful substances and then send the mail onto the office that deals with the claim.
When I am sending back forms they ask for the postcode and then tell me to send it to
Mail handling site 7, PO BOX whatever, Wolverhampton, WV1
its the first part "mail handling site number" that determines where its to go - that and your own postcode.
If you try sending it directly to Cardiff the Royal Mail will redirect it to Wolverhampton first before returning it to cardiff.
Monic