I'll put up a link to the above on the Linkedin groups and that should attract a little more attention for you.
What I don't understand is why don't you post out letters to people who received funding for that period via the various Universities they attended. The alumni organisations will have up-to-date contact information for many previous doctoral candidates and could forward such letters on (thus not disclosing information an alumni doesn't want them to) with details on how to take the surveys, either via an enclosed form or the website address.
The one thing I would advise above all else is anyone wanting to take a doctorate, be advised to talk over with a careers advisor their options and the potential effect on their career aspirations once they complete a doctorate. Many employers have a negative perception of doctorate holders, which can make job hunting difficult and even bar doctorate holders from certain jobs (i.e. overqualified, will get bored, will move on quickly as soon as something better comes along, etc.).
Ian (Mackem_Beefy)