I hate learning FrenchWatch
If you don't want to learn how to communicate with them (so as to insult them, obviously. Why else would they teach us French?) but feel pressured to do so by your family (who certainly must be dedicated to hating the French, to force it this hard. Real Roast Beef!) then don't learn.
Flipping the bird is universal, and certainly more than enough to drive any Frenchman irate. So rest easy, and explain to your family that you don't feel it necessary to learn French, as you have other means to carry out your purpose as a Brit.
Simply tell your parents that you don't feel the French are relevant in this current age (unless we invade/liberate them - in which case we shall encourage them to speak our mighty dialect).