Does the Queen tip her window cleaners?

Certainly does, she leaves an envelope out with at least 75p in it, same with the dustbin men and the paperboy.

Window cleaning is done by contract, no need to tip.

tipping for service is an American practice to make up for the poor wages in the country

actually it is an insult to do so as you consider the person a slave

The Royal Household is in charge of finances and payments. Tipping is not necessary for contract work.

she makes them a cuppa and gives them a hob nob

no, they are union workers

She, she tells them to back one of her winning horses.

we pay decent wages in the UK tipping is almost out of date in the UK

You must be joking she is so mean she saves old string.

They are on a government contract. There shouldn't be any gratuities flying about. Same with those who clean the windows in the council offices.

Yes.

Her windows are cleaned by palace facilities staff - they all receive a present at Christmas of a Tesco Christmas pudding.