I do think you'd need to speak to them, but you'd most certainly need a distinction at masters I'd imagine - the problem is that funding is so very competitive and you'll be up against people with 1st class BAs and distinctions at masters. Of course your proposal and references are extremely important and can sway things, but if it were a toss up say between someone with a low 2:2 and a distinction and someone with a first and borderline merit/distinction but the proposals were very similar in quality it is very likely that the applicant with the higher overall grades would be successful. Its very hard to guage it though - you may well be lucky but you'd have to clarify with them whether your performance at masters effectively cancels out the BSc.