Instant coffee is largely down to individual taste. I usually like anything from Douwe Egbert and I also think that Asda's own Rich Roast is rather nice.
However, up until last year, I could never understand why people sometimes raved about certain types of coffee in the same way that some people do about fine wines. That was until I tasted a coffee from a coffee cart in London. It was part of the 'Notes' coffee group, where they use a really light roast for their beans. It results in a much sweeter flavour than usual. (I'm usually a 'three sugars guy but I found that just one spoonful was enough for me, as it allowed the flavour of the coffee to really burst through). It was so good that I just had to buy a second cup - and then a third!
So if you're ever in central London, I thoroughly recommend seeking out Notes outlets:
http://www.notes-uk.squarespace.com/coffee/