The Corsa engines were developed by Lotus andmade 150bhp, then de-tuned with the rediculous inlet tract they came with from the factory so will always respond well to mods. The K4M makes 220bhp in the S1600 series and is a really well designed engine, has a good set of rods to take RPM and the head is well worked as standard. The inlet tract is crap and the cams are UBER mild. Wacky cams, solid lifters and a set of ITB's and it'll be MORE than capable!
When he's done it, tell him to give me a ring. I'll want to know how he gets on!!