Hi,
I too have a High Achievers Offer with Nottingham, but for MEng Hons in Civil Engineering. Have you decided that you want to Firm it? I've decided to do so, although I haven't sent my reply to UCAS yet.
Nottingham sent me an e-mail three months ago that said the offer on UCAS will be amended to Unconditional within ten working days of me making them as my Firm choice, and that the offer will include confirmation of my inclusion in the High Achievers initiative. ... Perhaps that applies to you as well?
By the way, I study Geography at A-Level.