Its rare to hear of Police Officers being charged to court mate. You must have some pretty strong evidence against them. I went through a similar situation last year, i too was assaulted and arrested for something i hadnt done but when i got to court the defence barrister tore me and my witnesses apart and it got dramatically chucked out of court. The problem was me and my mates had exagerated a bit in our statements, and when the case got thrown out we all ended up getting arrested for attempting to pervert the course of justice.... It wasn't a pleasant experience and i ended up getting some community hours and had to pay all the costs. If it wasnt for my solicitor i would have gone to prison.
Anyway my sister is a top solicitor in London. If i can give you any tips mate you need to ensure your statement is absolutely watertight and ENSURE that you DONT admit being drunk cos if you do your case could end up getting thrown out like mine did.
Anyhow good luck with it and let us know how you get on.