Thanks, fellow Locites, for your replies.
Yes, my car has a full LEXUS service history, which may help a teeny bit. Or not. I am also on the local Lexus dealer's service plan - however, they said "We will get back to you" and after four weeks of hearing nothing I emailed again with the appalling evidence in pictures. Still no response, although that was only two days ago to be fair.
I copied this from the Warranty & Service booklet (it seems to have come out huge - but you can read all of it if you click on it). Since it is obviously NOT "surface rust", the 12 year offer must apply. Hmm. IMHO, the bigger the company the more they behave like slippery eels - although to say I am disappointed with Lexus UK would be an understatement.
When I said I would put a wee video on YouTube if I received no joy, my trouble & strife said "I will put it on Twitter - and that'll waked them up!".
Ooh-er.