Well I see that 'your friend' has finally become you but, looking back through your previous posts, I'm surprised that nobody has provided the appropriate link. This is the actual document that judges must refer to:
http://sentencingcouncil.judiciary.gov.uk/docs/Assault_definitive_guideline_-_Crown_Court.pdf
See pages 3 to 6 for the sentencing guidelines (which judges MUST adhere to unless there are REALLY exceptional circumstances, which the judge must explain to the public in open court).
However, when reading that document, you need to be aware that the table on page 5 refers to sentences for first-time offenders who've been convicted after a trial. An early guilty plea can see a reduction in the sentence (by up to one third), wheras previous convictions (particularly for violence) can push sentencing higher; the maximum sentence for 'Section 18' is life imprisonment. Further, the actual time spent 'inside' is normally half of the nominal sentence (although, for sentences of 4 years and over, it can be up to two thirds).
So. if you're convicted after a trial, you'll spend a
minimum of 18 months 'inside'.