Where the RCUK OA block grant is used to pay Article Processing Charges for a paper, the paper must be made Open Access immediately at the time of on-line publication, using the Creative Commons Attribution (CC BY) licence. Find out more in the UKRI research policy.
For all other material: Use the Creative Commons tool to choose your licence.
The OAPEN-UK project published two guides based on a thematic analysis of the evidence given to the House of Commons and House of Lords inquiries and the responses to the HEFCE consultation on open access (Crossick, G., 2015. Monographs and Open Access: a report to HEFCE).
Both guides are CC-BY
When you come across work that uses Creative Commons you will see the distinctive Creative Commons logo (as below) and there will be a link to the licence under which it has been released. This tells you exactly what you are allowed to do with it.