how do you removed masking tape that has stuck to the windows

As above, but also try heating it up wth a hair dryer to melt the glue, then give it a good rub.

I would use a stanley knife to remove the tape from glass and if any residue glue remains try a little white spirit to neutralise it. Colourways Painting and Decorating Services

You can also get a spray can of "Sticky Stuff Remover" from Homebase, followed by using window scraper to reduce risk of scratching glass.

Use either a stanly knife blade or invest a couple of quid in a proper window scraper. You can pick these up in your local hardware shop and even some pound shops. The sharp blade should lift the tape no problem.

Krud Kutter. www.krudkutter.co.uk or any major supplier like brewers or TDS derby who will deliver for you. best of luck