Prior to the publication of new definitive guidelines relating to assault, judges were given this instruction:
"A sentence of 3 years� imprisonment should be regarded as a normal sentence for a deliberate wounding in which a broken glass or bottle is used as a weapon, in the absence of exceptional circumstances, even where there is a plea of guilty".
Source:
http://www.sentencing-guidelines.gov.uk/guidel ines/other/courtappeal/default.asp?T=Cases&cat ID=3&subject=WOUNDING%20/%20CAUSING%20GRIEVOUS %20BODILY%20HARM%20WITH%20INTENT
From the 3rd of March this year, new sentencing guidelines came into effect. The 'starting point' for a sentencing a first time offender, convicted after a trial, is now 5 years imprisonment, with a recommended sentencing range of 4 to 6 years. However, an offender who pleads guilty at an early stage can expect a 'discount' from the sentence which would be received after a trial.
Source: See page 13 of this document:
http://www.sentencing-guidelines.gov.uk/docs/a ssault-against-the%20person.pdf
Putting those two references together suggests a sentence of between 3 and 4 years imprisonment.
Chris