I know that there is no right or wrong answer on what, if anything, should be added to tea, as it is a purely a matter of personal preference. I have always found it interesting, however, that the overwhelming majority of people in the British Isles add milk to their tea -- even those who drink coffee black. When you order tea or have it served to you in someone's home, it is usually assumed that you want milk and is often already added to the tea when you get it. . Quite different from the States, where some add milk, some add lemon, and many don't add anything at all.
I like to add milk to the "breakfast" blends. Earl Grey I like plain and I usually don't bother with flavored teas. I must say that the strong blends favored in the British Isles do benefit from the addition of milk, and most packages of tea come with the suggestion "Best served with milk."
In reviewing the Twinings website, I found it interesting to note that they sometimes offer contradictory advice over how their teas should be drunk. Their UK site makes the following recommendation for Earl Grey:
milk, or with a slice of lemon.How and when to serve Black or with very little milk, but never lemon which detracts from the Bergamot. Some have it for breakfast, most in the afternoon, and some in the evening.>Best served with milk: English Breakfast, Earl Grey, Lady Grey, Prince of Wales, Irish Breakfast, Assam.
Best served without milk: Lapsang Souchong, Jasmine, Traditional Gunpowder, Darjeeling, herbal infusions, fruit-flavored black teas.