A masters is often used to transfer/focus more into a particular area and if your overall grades at the undergraduate level are not at a 2.1 level.
If you go straight from a BA/BSc a lot of colleges enrol students as an MLitt/MPhil for one year and then you transfer into a PhD if satisfactory progress is made.
Choose the college/lecturer after you have a research topic/idea and draft proposal for the PhD.
Colleges/universities vary in their areas of expertise.
Aphra.