Many British and some other universities offer intensive courses covering a whole range of topics during the summer months (sometimes, also in winter).
Please have a look at the list of summer schools on the website of the International Relations Office.
For some summer schools, there are stipenda available. More information can be found on the website of the International Relations Office.
Furthermore, each year, one student from Switzerland has the chance to win a stipend and a travel bursary for the Yeats Summer School in Sligo.