The antifascists held a rally outside the students union on the same day to celebrate that the fascists had been denied a platform. Some of the fascists heard about the rally and decided to head up the hill and attack it. No particular rhyme or reason for it, except that fascists believe in freedom of assembly for themselves but not for anybody who disagrees with them. There is more about this incident on http://libcom.org/blog/ and http://truth-reason-liberty.blogspot.co.uk
The local paper has done some research into the far right candidates and has found that the BNP candidate, Mike Whitby, lives in North Wales and can only stand for election in Liverpool because he has been renting a pigeon shed for 12 months. The National Front candidate Peter Tierney is a convicted criminal. He was successfully prosecuted for hitting a journalist over the head with a camera tripod. So one party is cynically manipulating election law and the other can't muster a better candidate than a thug. Somehow I don't see that working wonders for their chances of electoral success.