cheers for the advice guys.
toys19 – the form you mention may be handy, thanks.. I'll PM you.
Just to clarify a few things – firstly I've not actually submitted my proposal of 2 months notice and keeping deposit, to the landlord in writing. Unfortunately I know of my actual landlord only by the name of the trust to which the rent goes. All my correspondance is through an agency who are actually a friend of the landlord (and a commercial surveryors not a letting agency).
Secondly, although the landlord / agent would not know where I was moving to, they have my work email address and also know (very roughly) where I work. Furthermore, working in financial services (albeit in IT) I have to be very careful – I couldn't have an irate landlord approaching my boss for contact details etc.
Thirdly, my deposit is in the Govt deposit protection schemey thing..