Do you need a Master of Research degree to receive funding for a PhD?

Or likely need one?

I'm starting a taught Masters course in History in September and I'm thinking of applying for a doctoral research degree following it. I will likely be unable to fund the PhD entirely by myself, and so I will need additional funding. However I have heard that funding for PhDs is often limited to those with an MRes degree, particularly at Oxford where I was considering applying (I was under the impression that one simply goes from undergrad to Masters to PhD). Will I really have to do an MRes degree after my taught Masters to do a PhD? Thanks in advance.

Very very unlikely. Every PhD and funding opportunity is going to have different entry criteria. Some will specify a Masters, some won't. In STEM subjects it's more common to go straight from undergrad to PhD, but you're more likely to need an intermediate Masters in Humanities subjects. But even then, there are no hard and fast rules. In any event, I've not come across a PhD project or funding opportunity which specifies an MRes over an MA/MSc, and certainly none which require a taught Masters + MRes. Not saying they don't exist anywhere, but I've not seen one - and that would be such a fantastically specific PhD, that the requirements would most likely have been written with a preferred candidate in mind anyway,

Funding is more likely to be based on your academic track record in the first instance. It's very scarce in my field so without relevant professional experience, you need an undergrad First and Masters Distinction to even get on a long list. After that, it's like applying for a job - you need to be the right person for the project.

If money is crucial, I would usually advise against applying for advertised PhD projects which don't carry funding. It can be a soul-corroding experience. One of my Masters colleagues had to turn down six PhD offers - including one from Oxford - because they couldn't get funding. They were definitely good enough for the PhD projects, but didn't quite have the academic results for the separate funding sources. Hold out for a funded PhD whenever you can.

MRes degrees are pretty rare in humanities and I'd be surprised to see many places asking for them specifically. What is more common is to require an MA degree with a significant research component, which usually means a taught course with a research based dissertation required at the end for completion.

However, the amount of funding available for research varies hugely from year to year so I would not tie myself too much to a specific university / department. I'm currently doing a fully funded PhD in English (after doing just an MA which required dissertation), from my experiences applying and from what I know from others, if you want to get funding for a PhD you have to be strategic about what you apply for and be willing to change your plans if Oxbridge doesn't work out. One of my friends was really set on going to Oxford for his PhD. He applied after completing their MA but didn't get in so he did a second MA (in a different but related discipline), started corresponding with a prospective supervisor at Oxford and through them even managed to get an internship working as a research assistant on a larger projects. He was more than qualified and did everything right but after all of that they still didn't offer him funding. UCL did so he went there and is now very happy. I have a feeling he would have even been able to get funding somewhere else before the 2nd MA if he had looked at other options.

Does that mean that if I wanted to go straight on to a PhD after completing my Masters in September 2018 I would have to come up with a research proposal and have an offer of study by next January? Because that seems very early, given that I will only be about 2-3 months in to my Masters.

I have Oxford in mind more out of hope than expectation, but I don't want to rule it out. My Masters has a dissertation at the end as well.
I was wondering, many scholarships and offers for funding have deadlines as early as January. I know a lot of funding offers require the applicant to be holding an offer already. Does that mean that if I wanted to go straight on to a PhD after completing my Masters in September 2018 I would have to come up with a research proposal and have an offer of study by next January? Because that seems very early, given that I will only be about 2-3 months in to my Masters.