Many out-of-copyright books are freely available. Try the following sites:
Most public library authorities give members access to a range of online reference material. You can access much of this at home using your public library card.
Oxfordshire's Reference Online resources include:
Other public library services will provide similar resources. Find your lcoal library service on the UK.Gov website https://www.gov.uk/local-library-services
Access to Research is an initiative which provides free access to academic e-journals in public libraries. Note that you cannot access them at home, only in libraries. You can find a full list of partcipating libraries as well as information about the journals included on the Access to Research website http://www.accesstoresearch.org.uk/
OUDCE Open Resources http://open.conted.ox.ac.uk/ is a collection of freely available resources created or collected by OUDCE tutors. Your tutor may have created an area for your course and given you the link to it. If s/he hasn't, you can still use the collection to browse or search by subject or keyword for material on your topic.
If you are looking for information on the internet, don't just Google it! Whilst Google has its uses, you can end up with vast numbers of results, many of which are irrelevant. It can also be quite difficult to judge the quality of the information.
This page introduces some alternative ways of finding good quality, freely available information.
If you are interested in finding out more about searching and evaluating information on the internet in general, try: