Ok, I spoke to my friend today, he's a magistrate for the courts in Manchester.
Write to the police station and request a copy of the video evidence. They HAVE to give it to you, but you might have to pay £10-£15 to get it. If it doesn't show you going through on red, then absolutely go to court, and defend yourself. He told me if there's no proper evidence, the magistrate will throw it out of court. They won't trust the word of just one policemen with no evidence. What's more, if the video evidence doesn't prove anything, the policeman will actually get into trouble for lying!

However, should the video prove you went through the red light, he said you'd still get 3 points, but could get a much bigger fine, and have to pay £45 court costs.
It's up to you mate, but you need to look at that video, and ask yourself, hand on heart, did you skip a red light?