Interesting replies. Thanks.
While my intitial reaction was "well they should be prepared to pull up the stern anchor", first in best dressed has always been the way I've taken such situations so I most certainly was not going to raise the issue with the other boat. When we circled the anchorage checking it out I waved to the woman on board as we passed. Her only reply was a stiff "we have a stern anchor out" ... no wave no hello. I took that to mean imanarsehole so we moved off. Some folk simply let off an air of bad attitude.
There were btw no out of the ordinary weather reports. We had a SouWesterly that had been blowing for a few days and that anchorage was exposed to the south but it was fairly benign. They had been anchored there for a couple of weeks and had set the fore and aft anchors to keep their bow pointing into the direction of incoming wake from passing ferries and the like. I can well understand why they did it, but I confess I think it was a bit rude. They were obviously long term liveaboard cruisers. Young couple with at least one very young sprog.
Anywho, our decision to go elsewhere had more to do with the fact that we would have to anchor off their stern and a boat covered in nappies was not a view I fancied. To boot the other boat in the anchorage had run a deck mounted generator for hours on end when we were last there. We buggered off to a quieter spot , better protected and without the possibility of squawking sprog in the middle of the night.
“Give a man a fire and he's warm for a day, but set fire to him and he's warm for the rest of his life.” Terry Pratchett