I would say a 2.1 should be enough to get in, but you're best off contacting the uni. I've always received very friendly and fairly prompt replies when asking questions about entry requirements.
Nijmegen Cognitive Neuroscience info. Check their website. It's quite informative. You can even check the admission requirements, which tells you the type of knowledge you need for each track based on your bachelor degree.
Many postgrad courses are taught in English, even some courses station Dutch/English, with it defaulting to English if there are any non-Dutch speakers on the course.
Also, Phds over there are treated like jobs, you are paid for four years, and your pay increases each year. Much better funding. Also, even though the masters is 2 years, fees are €1,771 for the year for 2012-2013. Cost of living is cheaper, at least cheaper than London.
Hope this is helpful. I wish I were in a situation right now where I could make the move and start this masters.
As for the fee difference, well you are treated like a home student. This is why I know many EU nationals who have opted to complete a degree in their home country and then do an Erasmus, where you pay fees to your home country.