Principle one: Maintain your airforce. Germany can annihilate your entire navy, and there is nothing you can do about it. So, you have to specialize in the two units that can cross water and also cripple Germany. Don't be afraid to spend money on technology, as heavy bombers and jet power can often mean the difference in a close game.
Principle two: If you have a transport left after Germany's turn (stranger things have happened) then use it to ferry something over to Africa while you still can, because chances are it won't survive another round.
Principle three: Return the favor. Keep the German navy in check. It works both ways, and in this example the United Kingdom has the upper hand, because it's likely the German bombers are either busy with Russia, or have been shot down already so you can keep pounding Germany's ICs, with little retaliation.
Principle four: Protect Karelia. If the need arises, send fighters to defend the valuable piece of real estate, as in my experiences a fallen Karelia means a weak Russia, which means a strong Germany, which means a dead U.K.