Has anyone bought patio doors off the internet?

[IwishIwerewitty]

We have sliding doors in our kitchen that lead out on to the garden. We don't really like them and want to change them.
We had a quote yesterday for supplying and fitting new patio doors with side panels (they are big at 2m x 2m) and this was about £1700.
I have had a look on the internet and we can get some supplied for under £600. I haven't spoken to the company yet, but will do this morning.
This is obviously much cheaper, but has anyone else done this?
I would need to get someone to fit them - what tradesman would I need and how much would I expect to pay?
I was just wondering if it is a great way of saving money or will it end up being too much hassle?
Thanks.

did the quote break down teh costs? it is always good to get a few quotes anyway. yes i think getting them of the internet and then fitted would end up being a big ole hassle.

We got our patio doors from Wickes and had them fitted by a local joiner. We are really happy with the result.

thanks guys.
I have just called he company and they said roughly £600. Trouble is we need a cat flap fitted and they can't do that, but the others could. Will keep on looking and comparing. It's getting the balance between getting a good job done and not being taken for a ride.