as for sources of papers:
I have read a few relating to GABA (sleep issues) from the Journal of Psychopharmacology, they were all informative.
If you are at a university (idk how things work in the UK) you should be able to go to the university library and have access to some online journals through that. Look on your library website for sections about doing research, searching journals, etc.
Here in the states most universities have access to things like Academic Search Premier, EbscoHost, Science Direct, SpringerLink, etc. These are essentially search engines for scholarly articles in hundreds to thousands of journals, such as the Journal of Psychopharmacology, or The British Journal of Clinical Pharmacology.
So fi you are looking for proper medical articles, your library at university can probably be a good place to help you find them. A lot fo the citations on wikipedia will lead you to an article that you may not have full access to (if you try to look at it from your house),but fi you are on a univeristy network, and your school has access to that particular journal, then you should be ok to read the full article.
hope that makes some sense.