Im not even at university yet!
But if I were you, I would sit down and get familiar with all the modules you are to sit next year and see how realistic it is to achieve a 2:1 overall based upon what you have got so far and what you are likely to achieve with a lot more motivation!
Then after doing that, I would see for any possible transfer universities. Its ashame to not complete your degree at Brunel because of it being a good reputable university to obtain your degree from. After seeing the other possible candidates you have to way up the following:
Is it worth risking to get a 2:1 from a more reputable university, which your currently studying at Brunel. Or is it worth transfering to a different university, with more confidence of achieve the 2:1 but from a university that does not hold a much reputation.
Hope that made you think about things more clearly! No one can answer for you, the ultimate decision will have to be made by yourself!
Good Luck and hope you get it all sorted.