Just a couple of points, chappy:
...what sentence is my attacker likely to get when found guilty
I think you might be better off if you considered what the sentence might be IF he is found guilty. Proof has to be presented to the court which proves the matter beyond reasonable doubt and if the prosecution is going to trial there is, alas, the possibility that the verdict may not go in your favour.
The other prosecution witnesses obviously help your case but the fact you sustained injuries does not prove they were inflicted as result of an assault, it does not prove who inflicted them and it does not prove whether they were inflicted as part of reasonable self defence.
As far a a possible sentence goes, the maximum sentence for common assault (which I assume is the charge as you have not said otherwise) is six month’s custody, though many first time offenders are dealt with by way of a conditional discharge or a fine. It surprises me that the charge is common assault in view of the severity of your injuries. This may aggravate the matter quite considerably and may lead to the sentence (IF a conviction is secured) being racked up to a community order.