As former Membership Secretary I can answer this one.
1 Year Membership is £18
5 Year Membership is £72 (that's a 5-for-4 concession from AUK)
but while the overseas postal supplement is £9 for one year (which is still a bit of a bargain), the 5 year supplement is £45. Which is as it should be as our mailing provider doesn't give us any concessions.
That answer should probably be added to the
join us page with the rest of the Fees information, as I'm sure it will be before too long now you've highlighted its omission, for which thanks.