George & Bill
semiotically superfluous
This - a nice letter saying that you were sorry not to have had the opportunity to speak to them, and that you'd really appreciate their bearing you in mind if a similar position comes up. Shout them up again in a few months, reminding them that they had already agreed to interview you, and send another copy of your cv. Recruitment is time-consuming and expensive and if there's an oven-ready candidate, lots of companies will go to them first.
And have a word with that agency. That would royally rack me off.
Try and agree on a timescale for getting back to them before they move onto someone else.
This is definately what I should do. At the moment, thought, having just recieved an email from the deputy head tacitly revoking any admission of fault, I'm having to resist telling them I plan to tell all my friends and contacts to stay well clear.
I've started sounding like people's mums.