The offence you describe falls under Section 2 of the Sporting Events (Control of Alcohol etc.) Act, 1985.
The maximum penalty is a fine of �500. However, a Discharge (Conditional or Absolute) is also available and, in exceptional circumstances, Community Rehabilitation or a Curfew Order is also an option. The most likely outcome for you is either a fine or a Conditional Discharge.
However, more relevant to your question is the fact that unless they order an absolute discharge (which is unlikely) the Bench MUST consider imposing a Football Banning order. It must decide whether such an order �...will help to prevent violence or disorder occurring at or in connection with any regulated football matches.�
If an order is imposed it must be for a minimum of three years and a maximum of five years. The order will prevent you from attending any regulated football match in England and Wales, and may also prevent you from travelling abroad to attend such matches as fall within the meaning of the Act.
You must hope that the magistrates see your offence as minor enough to persuade them that an order is not necessary. If, as the Reverend seems to suggest, you are of previous good character, this will help considerably, as will an early guilty plea.