Don't park at the Ricoh! It was a tenner a go last year. Park at one of the Car Parks just off the M69 and walk in.
Better parking advice. If you take the turn off the island opposite the Richo stadium (dual carriageway) and then take the first left (under a railway bridge) into Holbrooks, there's loads of street parking in a fairly safe part of Coventry - I work for Jaguar and used to work at the Radford and Browns Lane plants and know the area pretty well.
Was £12 in some of the places last year and most of the surrounding area seemed to be permit holders only parking, ended up doing a park and walk job at this pub, just up road from stadium 3 quid i think. Straight up this road across from stadium and yer turn left at railway lines, only a 10 minute walk or so, but you can see the ground cos its just one long road down to it.