@phoneboy I always buy PG Tips tea bags for my trad tea drinking rellies. For myself, I don't drink much tea, but when I do it usually comes from nbtea.co.uk and is Smokey Caravan or Silver Needle (often with jasmine).
Jackson’s of Pickadilly would be a good choice. Earl Grey or Lapsang if you like your tea messed about. I like Darjeeling for "straight" tea, because it tends to be more delicate. Kenyan is stronger and I’m a weak tea drinker, but it's popular. Englis Breakfast tea and other such blends are probably the most popular. They're blended for drinking hot, with milk.