The plastic liner cups that Derek UK mentioned earlier, seem to give a good solution to increase the articulation of the mirrors.
Have now fitted these I would say it is much easier to get the mirrors into the best rear vision position. Also being black plastic they are almost invisible when fitted and have the benefit of making a better (soft) fit on tightening the adjustment screw on the back of the mirror frames, which seems like a win/win.
Details below;
http://www.ldparts.co.uk/shop/shop.p...0&sid=sidd6fb2