The reason they always want you and your partner there, is so that they avoid the old '' ok thanks for the quote, i'll have to speak to my partner first'' response!

They basically want both decision makers in front of them so they can try and 'close' you there and then.

Personally, if you have an Anglian Windows near you, they are the people i would highly recommend. They aren't the cheapest, but you get a 10 year guarantee, and they are a company that have been round a good amount of time to be able to back up what they say they will do.