All instant coffee has a nasty aftertaste and I just don't like it. I generally stick to Lavazza, usually the red ground one or the espresso version. it needs to be drunk soon after brewing whether prepared filter or espresso, and I like it strong and black with no sugar. Supermarket own brands I've tasted are all inferior. When it's on sale in 3 for the price of 2 packs the Lavazza Red is no more expensive than supermarket brands.
HOWEVER I really can't understand the difference between a Sainsbury's basic cauliflower and a standard one, except for the price. Same goes for other vegetables and fruit.
I go to Waitrose when in Wellington specially to buy one of their own-brand tapenades which is IMO superb, but agree with comments above for most of their own-brand things, often bought by some family members.