Others have already referred to my previous posts. However the sentencing guidelines have been recently updated.
The use of a glass as a weapon probably pushes the offence up from 'Category 3' into 'Category 2'. That means that (for a first-time offender, convicted after a trial) the court must (other than in extremely exceptional circumstances) pass a sentence of between 5 and 9 years custody.
However, if your husband pleads guilty at the earliest opportunity, the sentence could be reduced by one third. So the sentence passed would then be between 3 years 4 months and 6 years.
The time actually spent 'inside' is normally half of the nominal sentence, so it's likely that your husband will actually be 'banged up' for between 1 year 8 months and 3 years. (A four year sentence, meaning two years 'inside' is the best guess I can give, based upon the limited information available).
Here's the actual document which the judge must refer to when considering sentence:
http://sentencingcoun...ine_-_Crown_Court.pdf
Chris