I must admit I thought this was a joke when I first saw it. But I soon realized that that you are actually serious, which lead me to conclude you are by far they most ignorant bunch of people I have ever read about. I'm not even really sure where to start telling you you're wrong. Mainly you have failed to mention the fact that most other states which had colonial empire were more brutal that Britain. The Russian, Japanese, German and Italian empires crimes make Britains pale into insignificance. And in fact it was the massive cost of fighting these rivals which ruined the British Empire. Britain did the right thing regardless of the cost; and gave up her power to save the people of the world.
I am not disputing that things could have been better, but so much was given to the world by Britain that has change it for the better: Common Law, Representative assemblies, ideas of liberty and much of our modern technology, buildings, engineering and science. Unless you want to give all that back you will not even get an apology.
You have also failed to realize the absolute absurdity of you request. 31 trillion pounds, when i read that i laughed so hard. If you honestly believe one of the most powerful nations in the world and an a people who have given the world so much would consider that then you are even more ignorant that I thought. I'll make a deal with you, if you get us reparations for the Roman, Anglo-Saxon, Danish and French invasion of Britain, then i'll buy you lunch.
Good luck wasting your life, i'm happy in Britain with all my stolen gold and 'bad inventions'.
Matt.