Sounds like the timing got screwed up after the vanos job.
Are you sure it was the vanos causing the no start in the first place? I think there might be two problems now.
Lesson to be learnt: Don't let someone learn how to time a BMW engine on your car. Take it to someone with experience with these engines, even though it is not hard, not everyone has the tools or how to to do it and can screw up.