Just caught up on this thread. I get the impression you might be based in the UK. If that is the case I cant imagine that in your line of work there would be a non beard policy and so the opinion is the managers and not the companies. As long as you keep it tidy I cant see that you will have any problems. If the manager says anything again i would just take him aside and have a quiet polite word with him. When challenged in this fashion people usually back down.

Being bearded isnt always easy, but it is always worth it