If we had any of these in Forest Hill I would gladly give it a try. Since we don't I will continue to buy fish from Sainsburys (vacuum packed means I have never had a problem with freshness, probably fresher than a fishmonger where the fish is left out all day).

I don't think supermarkets have the monopoly on keeping Vegetables and fruit on display that will not last long. I found the same problems with plenty of produce when we did have greengrocers in Forest Hill (20 years ago) or when I had a greengrocer round the corner (in Edinburgh). I reckon the freshest fruit and veg comes direct from a farm or is air-freighted, buying English produce in a supermarket is worst because too often the produce is picked when ripe and packed for fast consumption but it takes too long to reach the shelves.