How friendly or unfriendly in London Metropolitan Police?

I stayed at a hotel near London Heathrow Airport for approx. 15 days at an average rate of �50/day including VAT. While checking out, I was asked to pay �500 for a liitle additional cleaning effort. I found the stated amount to be too high and resisted payment. I strongly suspect that the manager of the given hotel has some arrangement (either periodic bribes and/or special discounts) with an officer of Metropolitan Police who initially threatened me regarding Criminal Damage. After finding no evidence to charge me against any offense, he bluntly told me that he can detain me for 24 hours without any charges whatsoever. I had to pay the given amount to avoid further delay and inconvenience. I was a victim of Blackmail and Extortion using the Powers assigned to Police (most like bribed by the Hotel Management). Are police officers in UK above the law?