The Research Councils UK document on open access is here.
To summarise, it imposes the following requirement on publication of research funded by UK research councils: it should be published in a journal compliant with the RCUK open access policy, meaning primarily
The journal provides via its own website immediate and unrestricted access to the publisher’s final version of the paper (the Version of Record), and allows immediate deposit of the Version of Record in other repositories without restriction on re-use.
The requirement comes into force in April, sooner than I had expected; but there is a slightly weaker version as a get-out.
I have argued ad nauseum that the Diamond Open Access model is the best way to achieve this, and I am pleased that the Australasian Journal of Combinatorics includes on its web page the statement that, from the start of 2014, it will be compliant with the above strong form of the RCUK policy. So EPSRC-funded researchers can safely submit their papers to the AJC.
Go to it!