I'm from the US so maybe not what you're looking for, but for black tea you need a few things:

• 212° water (freedom units) - must be boiling, not boiled-then-left-to-cool. I use an electric kettle. If your water isn't hot enough your tea won't steep effectively.
• Decent tea. If you're steeping 15 minutes you might be drinking cheap tea made with fannings (essentially the tea dust that's left over after the better quality products have been packaged). I drink Yorkshire Gold but this is a matter of preference.
• Milk and sugar to taste, but these should complement the tea. Tea should be the predominant flavor, it shouldn't just taste like milk or sugar.

Here's what you do:

1. Heat the water to a rolling boil.
2. While the water is still boiling, pour over the teabag. Pour slowly enough that you don't rupture the bag.
3. Steep for 5 minutes.
4. Remove the teabag. Don't squeeze it out - this releases more tannins and your brew will be more bitter.
5. (CONTROVERSIAL!) Add milk and sugar. Some people will tell you milk goes in first. These people are wrong.

Some people will talk at you about teapots and patinas but honestly if you're an infrequent tea drinker it's not worth bothering with.

Signed - an American anxiously awaiting all the UKians who will tell me I'm doing it wrong.