Very few football-related offences end up with a custodial sentence but it does depend upon the circumstances. Throwing a single missile in an isolated incident might not be taken very seriously but taking part in a near-riot will appear far worse.That principle has actually been stated by a judge (forming a legal precedent):
"A feature of the offence is that it is not the individual conduct of one offender that is of importance but the nature of the offending as a whole"
'Violent disorder' is an 'either way' offence, meaning that it can be dealt with by a magistrates' court or referred up to the Crown court. Unless you've exercised your right to insist upon trial by jury (which seems unlikely, as I assume that you'll be pleading guilty) the usual reason for to case to be 'referred up' is because the magistrates believe that their sentencing powers will not be sufficient. (So the magistrates were of the opinion that a sentence exceeding 6 months might be required). However Crown courts frequently impose non-custodial penalties after an 'either way' offence has been 'referred up', so there's no reason to assume that a custodial sentence is inevitable.
If you've got a good barrister I still think that there's a reasonable chance that you'll be given a non-custodial sentence (or possibly a suspended prison sentence).
Many offenders don't even get to meet their barrister until a few minutes before they appear in court. You need to seek his advice well before then. You should INSIST that your solicitor arranges a 'conference' meeting, where you'll see both your solicitor and barrister together.
See also here:
http://www.cps.gov.uk...ual/violent_disorder/
Chris