Due to engineering works, Coventry City supporters from Coventry are advised not to use the train for the Sky Blues game at Gillingham on Saturday August 25th from Coventry station.
Buses will replace trains between Coventry and Birmingham International / Nuneaton / Leamington Spa from Saturday August 25th until 12:00 on Monday 27th August. -http://www.nationalrail.co.uk/service_disruptions/192548.aspx
Also, there are no trains to or from London Euston from Saturday August 25th to Monday 27th August.
One option would be to get to Leamington and get the train to London Marylebone and then the underground to London St Pancras and the train to Gillingham.