Look, Mat, no one can come on here and give you a definitive answer to "what will happen?". Let me explain why:
You have given some details, however, without actually knowing the full facts it's impossible for anyone to guess the likely outcome, not least because none of us is involved in your case, nor will be trying it.
I'm not criticising you by what I'm about to say, however, had you asked opinions about the sentencing guidelines for, say, ABH, then that's quite simple to find by just looking it up on the net. For example, check out this link:
http://www.cps.gov.uk...g_actual_bodily_harm/
That, though, is merely indicative of what could theoretically happen to you if you end up being convicted at court of in this instance, ABH. It does not take into account all the other circumstances surrounding the case, i.e. what other charges have been brought, who saw what, who did what, who said what, so on and so forth.
Hopefully, you can see the complications involved? I'm assuming that you had access to a solicitor during your time in Police custody? S/He would be able to advise you a lot better than all of us because s/he will have a far better idea of what happened and would have access to most of the evidence available. So, speak to that person as a first port of call. Failing that, don't be afraid to try to contact the Police Officer dealing with the case who may be able to give you the benefit of their experience and let you have an informed guess.