If you're looking for any sort of support for your PhD, and serious about possibly getting a job in academia on teaching and research side, you might want to think about making sure your MA diss leads into what you want to do for your PhD. In History, at least, admissions and hiring committees like to see people whose work is focused enough that it will be feasible for the applicant to produce on the scale that the REF wants, and that will attract students. I'm not saying breadth is discouraged -- far from it -- but a research agenda that is coherent and feasible is becoming ever more important. Getting published in the right places is really difficult unless you've started to carve out a niche for yourself.