I'm sure Mark is right. The other thing about heather is that it is a very delicate plant, though you'd never believe it if you hit a ball in there. It's very easy to kill it or to allow other, more aggressive species, to out-compete it.
They are planning a bunker renovation project at the moment; the idea is to return the bunkers to a more historic look and feel. Someone said to me last time I was there, in December: 'The only bunkers that look right are the ones that are no longer really in play' (ie they are Fowler's originals, not the ones that have been added more recently).
I'm going to a seminar tomorrow which Chris Lomas, the Berkshire's head greenkeeper, plus a lot of other greenkeepers from the top heathland courses will be attending, so I'll ask him for his thoughts.