Theres Red alert 3 aswell as the CnC ps1 games in the uk psn store. Endwar is out on the ps3 aswell. Theres a really good one thats half rpg or something aswell that a lot of people on here have played but cant remember the name of it for the life of me. Might not be your thing if your just after a straight up rts anyway.
There is a version of Civ, Civilization Revolution.
You know what, I hear a lot about CnC games and I think I got about £10 on my PSN Wallet so I could probably buy it but I've never played a CnC game before (lol I know) I've always prefered the traditional medieval looking games but everyone tells me CnC is amazing ,is it worth a try? What is it about?
Could try Ruse. It's a WWII RTS - there is a demo on the PSN.
You can download the original C&C as well as Red Alert and Tiberian Sun & the Firestorm add on pack for free, legally.
http://www.commandandconquer.com/classic