The EH press office is 020 7973 3000, I have spoken to them before with other queries. Not much she can do obviously apart from refer to the 'right' person, but enough calls from enough people, maybe mention you are press, should give them enough pressure to at least start getting nervous, maybe even act. Maybe question the nature of the relationship between Tarmac and EH in regards award sponsorship and lack of action. It is sometimes too easy to ignore emails, yet a phonecall is difficult to ignore, especially if there are many of the same nature.

hope this helps,

johan