Where can I get reconditioned kohler engines?

I need a rebuilt or reconditioned Kohler Magnum 18 engine for my (American) YardPro garden tractor. Preferably in SE England. Alternatively someone who can repair these engines (cost effectively!).|||Do you have any ARGO dealers over there.Check that out or Google it.|||try www.tillerparts.co.uk(or .com) guy called Chester does lots of makes of old agricultural machines,the howard gem used a kohler a one point,good luck!