Matt
As you know I live 24/7 in ht eUK and play most of my golf here. I can't think of a bunker that had gorse or anything plant-like growing in it in all my 25-30 years of experience playing here. You must have been unlucky, or maybe you hit it so far you have found bunkers that I never knew existed?
My point was that when you have bunkers which entail too much of a penalty, the experienced golfer will avoid them, and they become non-hazards, just eye candy, and the strategic options of playing the course are diminished. You might as well turn the bunker into a pond, like they did on the 16th at Garden City....
The same holds true when the bunkers are naturally penal (without vegetation). Experienced and/or good players will avoid them like the plague (viz. Tiger in his last 3 Open wins), so they become impotent and irrelevant.
PS--as I think I said above, gorse (and broom) does not naturally grow in pure sand. It need sturdier soil to prosper. Marram grass does grow in sand, but I do not even think that a golfing stgud like you would like a regular diet of hitting out of sand infested with marram. Just think of the right hand side of the 8th at Cypress Point......