I filled in the "Contact Us" form on the WebSite, and received the following reply:
Thank you for your email.
I confirm I have upgraded you to Five Star as you have 10 rentals on your
profile.
I think all the rentals have been registered under your Gold number,
however you did not sign for Gold Service in the US, Canada, New Zealand
and Australia.
Please go on-line, update this, print the form and send it back to us to
the contact below.
My profile on hertz.co.uk now says "Hertz #1 Club Gold Five Star Member", woo woo :-) It also says "We've noticed that we still have not received your signed Hertz #1 Club Gold Agreement. Click here for a new printable copy." - it definitely didn't used to say that! So I'll sign and send, and it looks like all my problems are over.
Well, apart from the fact that I still don't seem to get any "Hertz Points". Are these US only?
Thanks,
-simon