You might want to look at Leko's games as he is a big champ of 1...c5

It might be old but Watson's efforts on 1...c5 are worth looking at.

a good pick would be Richard Palliser's "Beating unusual chess openings", he advocates 1.c4 c5 with the intention of playing a botvinnik setup (pawns c5-d6-e5), otherwise known as The Longhorn. Indeed it seems to be more equal for Black than for White! Some good reasons to give it a try :
- Black starts with the simple plan of trying to raise the longhorn, and RP makes it clear when it is possible or not, and what to do instead. Of course, that being achieved, the position is equal ;
- 1. Nf3 c5 is convenient il you like to play the sicilian ;
- some English players noticed that while they consider it a clean equalizer against Nf3-c4-g3, some popular books for the White side fail to give the best moves for Black. Check this out!

A slight warning : in order to spice things up a little, RP offers a nice variation, but it works only if White carelessly omits a2-a3 in the opening; you may call it a "dangerous weapon". But a careless English player can't really be an English player...