Sentences for GBH with intent?

my partner & myself had a few drinks & went out, we ended up having a fight, & he bit my face biting a hole in my cheek which required a 2 hour operation under general anaesthetic in a plastic surgical theatre he has been charged with GBH with intent, all this happened while he was still on licence after only being out for 10days from serving almost 3yrs inside, it all just seemed to happen so quickly & i feel that really he didnt have time to even settle down properly,i have since then dropped all charges against him as i don't want to see him locked up for 5yrs or more, & he has to appear in court & does not know whether to plead guilty or not ?, we are still together as i have forgiven him & still love him & wish to get on with our relationship, can anyone give me any advice on what the sentencing may be ?, he has just turned 24yrs old & he served 3 yrs for a robbery