what sentancing can i expect for my 18 yr old son charged with section 18

[rowantree]

My son was punched in a pub by very drunk racist person who has extensive public affray criminal record and is well known by the police to be part of a violent local gang. (he was tagged at time of fight) and since the incident has been charged with other offences. My son over reacted and hit him over head with bottle he was holding at the time, a fight then followed with other people getting involved. My son sustained injuries to hand requiring surgery, but the other lad unfortunatly had a wound in his armpit which nearly lost his life (although it didn't stop him from kicking a police women in the head, who was giving him life saving medical aid) he continued to be very abusive to the paramedics and hospital staff. Unfortunatly my sons friend was threatened by gang members to keep out of it or else. (He has since been assaulted once and has recieved death threats) His freinds claim my son initiated the assault by deliberatly picking up a bottle, hitting him over the head then stabbing him with the bottle neck, my son didn't know him and has never been in trouble with police before. My son had no intention of hurting the other boy. The other boy , a white lad had already picked a fight on another black lad the same evening by grabbing him by the throat (this lad has admitted this happening to the police but is too scared to prosecute). And we believe it was a racially motivated attack on my son in the first place. The other lad was shouting many racists remarkes heard by the medical staff. Unfortunetly the CCTV is worse than usless, and my son is being charged with a section 18. We have been told that despite the witnesses being friends of the other boy their statements are still valid and will probably be believed, as it is effectively my son's word against all of theirs. What likely sentance can we expect and how will it affect his future?