At the time of my MA (2004) and PhD (2005-2009) my research area was late 20C Continental Philosophy and more specifically phenomenology and post-structuralism. As you may be aware many philosophy departments do not consider these approaches to be suitably ‘philosophical’ enough to offer supervision in them. Consequently my MA was done in a Politics department and my PhD in a Sociology department both at top tier UK universities. However my undergraduate degree (1999-2002 Australia) was a double degree in Religious Studies and International Relations. Changing disciplines after my undergraduate degree did not present any kind of problems for me at all as administrators and supervisors were mostly interested in my undergraduate performance coupled with the letters of recommendation written by the Australian academics from my original university. As you say you have these areas covered then I can’t see changing disciplines being a problem and I encourage you to follow the lines of study that animate you the most.