I have already tried Tesco and other supermarkets a number of times but no luck in finding a selection of 'dry' white or red wine
Pure nonsense - you must not be looking close enough for some reason then as Tesco for sure have got a wide selection of Pinot Grigio, Shiraz, Cabernet Sauvignon, etc. Just look or ask for 'Wino
Wytrawne' under country and colour of choice.