2006 320d...what's considered good value?

[Cootehall]

Having considered various options I've narrowed my search for a car to a 320d SE. It's primarily for commuting 20K p.a. I figure getting a used 320d is worth the investment over the albeit attractive rep mobile offered currently knocking around. Anyone have experience of recent deals for a 320d? Where should I pitch my budget at? My idea car would have <20K on the clock beyond that I'm happy enough with a straight SE.