(As I understand it, most of the Highway Code itself does not have legal force, however, should an accident occur where one of the parties involved is in violation of the Code, this is likely to be taken into account when determining their culpability with respect to a charge of Careless or Dangerous Driving.* I have to admit that I'm not certain on this though. Corrections from those in the know welcome. While I think a law about giving cyclists room when overtaking is unnecessary, I would be very happy to see such a provision incorporated into the highway code.)
* We like to think of it more as guidelines.