Its right, nobody will be arrested until you've actually made a complaint to the police, they'll then take a statement off you and depending on the area, may seize the cctv, which can help evidentially when both parties are drunk. what a person is charged with all depends on the injuries you recieved and the intent of the offender, the fact that you've spent 4 days in hospital means that the police can send off for medical evidence which can be used to charge for a more serious offence, and which the CPS will require before they make a decision on charging, that is, if the "threshold test" has been met and the file goes as far as CPS. In some cases, if the evidence is not reliable or there is no realistic prospect of conviction, then the case can be dropped by the police.