The NIHR has a new open access policy which came into force in April 2014, and have recently issued some guidance to clarify what publications are covered by the policy and how any associated costs should be paid. 

The policy can be found here:

In summary, the policy applies to only one, main publication describing the findings of an NIHR funded project.  A project published in an NIHR Journal would normally be considered to be the main publication for the purposes of the policy.  It applies only to projects that complete after 1 April 2014 and to articles published after 1 April 2014.

Publication costs for other publications related to the project will only be covered if they have been agreed in advance, by the NIHR, as part of the project funding application process.

The NIHR also expect that where a project has been funded jointly by the NIHR and other funders, the majority funder is expected to pay the appropriate APC if that funder has an open access policy.  This does conflict with the policies of some other funders, and so if this is the case advice should be sought from RIN.

Researchers receiving NIHR funding should be aware that the NIHR has an agreement with BioMed Central (BMC) that reduces the APC for NIHR researchers publishing in a BMC journal (though this does not mean that the NIHR recommends publishing in a BMC publication).