Sadly, public funding from the AHRC is diminishing, as are universities' own funding, IME. So if you're looking for an academic job after your PhD (also a shrinking field), having an AHRC studentship is evidence of your ability to attract external funding for your research.
But a PhD is a PhD. If you go to a good Department, with a supervisor who's committed to her PhD students, then you'll be taken seriously. IF you do the work in the way that's required, of course! Doing a PhD is a huge step up from an MA, so be aware of that.
Ask around current PhD students (at research seminars and so on) to find out about supervisors in your field. Tough is good, "Doesn't suffer fools" is good - as long as that is matched with commitment. That is, that your supervisor will read work in a reasonable time frame (I usually ask for at least a week to read a chapter, and a month to review the thesis as a whole), and is able to meet regularly with you: about once every 3 to 4 weeks during term-time is what I aim for with mine.
The main caution that humanities university departments have with self-funding is that students tend to take too long, or drop out, or not finish. Be aware of the stringent standards we are held to: completion within 4 years full-time, or the part-time equivalent (which isn't always twice the time of full-time, BTW). Departments are sanctioned if completion rates drop below something around 70-80% (the idea is that we kick our students along - "robust" supervisory practices).