Hi all,
Don't know if this is helpful to anyone but just to let you know that as of today (Aug 2012) the only mortgage lender I have spoken to who will accept PhD stipend income in a mortgage is Lloyds TSB.
Natwest will only accept a small amount of it (e.g. 1/4 of it) and even then I think you have to have a co-applicant.
All the others have said NO immediately... grr.

Hope this helps anyone searching the forum in the future, or even now...!!