Fianchettoing the bishop to b2 signals the Colle-Zukertort (versus the other variation known as the Colle-Koltanowski).
The Gruenfeld is an acceptable response, I believe. You can check the Openings Explorer here to see more on it.
There are also a couple of recent books on this variation for White. Zuke 'em, I believe is one of them.
Someone at the local chess club plays the Colle System ( or is it the Zuckertort?)
it is sort of like a london system with the DSB on b2.
How do I play against it? I am a Grunfeld player, BTW
Thanks