I'm sorry there's a tendency for requests like this to be met with abuse from certain people.
I think they must get a self-righteous buzz from it - I can't think of anything else they might hope to achieve.
Lets see if I can be more helpfull
From the Governments' sentencing guidelines:
Stabbing
AG�s Ref. No. 18 of 2002 (Hughes) [2003] 1 Cr.App.R.(S) 9
� Having referred to a number of existing authorities, the Court concluded that,depending on the circumstances of the particular offence and whether or not there is a plea of guilty, a sentence within the range of 3 to 8 years was appropriate for offences contrary to s.18 of the Offences Against the Person Act 1861, when a knife is used.
Current Sentencing Practice Reference: B2-2.3A
The recommendation for erduction for a guilty plea is 1/3 if he pleads guilty immediately, 1/4 if he does so after a trial date is set down to 1/10 'at the door of the court'
There is a lot of interest in knife crime at the moment and as he has a record of GBH and as he's only avoiding a murder charge by sheer luck I think he's probably looking at the upper end of that range.
Of course a longer sentence makes an early guilty lea worth that much more time.
You also need to do some thinking about whether this is the sort of man you want to spend the rest of your life with. Loyalty is very admirable but even if he never lays a hand on you there's a good chance he'll be in and out of gaol all his life.
Personally I'd think it'd be better to break with someone at the beginning rather than wait until he's had 3 or 4 years of fretting about whether you're waiting for him.
But it's your life