use the findamasters site to search for the MSc courses. You can also use the UCAS site to find out which universities are active in psychology. Another way of find the course you want is to decide roughly what uni you would like to go to and look at their site.
Another way would be to look on the times higher ed website, you will need to register for a free trial (but you get sent a free newspaper!!!). These have university performance tables, and i believe that there is a table that shows which universities are best for pyschology, and in general the better uni's will offer the best MSc opportunities. I hope this all helps, best of luck