Ask your current Department. Which field are you in? Broadly, Humanities or STEM? I can give an overview of Humanities funding.
National, competitive funding for Doctoral programmes in the Humanities is via the AHRC Doctoral Training Partnerships. And funding for PhDs starting in September 2017 is now decided.
Funding is highly competitive. You need to start thinking about your PhD proposal in around November of the year before you wish to start - talk to your current tutors/MA thesis supervisor about a suitable project.
You'll need to write a really good, argued, concise thesis proposal - 1,500 words usually.
You'll need to be in contact with your proposed Department's Postgraduate Research student Director, and possibly a potential supervisor - it's good to be in contact personally. Application to a PhD programme is a very personal, tailored thing.
You'll need to think about why you're applying to a particular place. Match Person, Place, Project (3 Ps). It's not a random thing.
You might also want to think about what your aims are after a PhD. Do you want an academic career? Remember only about 50% of PhD graduates go on to do this (and I suspect the job market is about to contract seriously). Where you do your PhD WILL make a difference. I see it in selection committees for entry-level lecturer posts: there are some places in my field which produce excellent Doctorates, and others that do not ...