There are a couple of things to bear in mind when you are searching for online prices for double glazed windows & UPVC Front Doors and those are to do with quality, workmanship and, of course, value for money. See more info Here: www.finddoubleglazingprices.com
The quality of the materials cannot usually be judged without making some kind of comparison, so if you are getting quotes from an installer, ask to see actual samples of the windows. The quality of the workmanship can be judged somewhat by also viewing previous work carried out by the installer, but you should also make sure that there is a good workmanship warranty attached to the contract in case there are installation issues and most importantly that the warranty covers the installation for a suitable period after the job is finished.
In terms of value for money, get at least 3 separate quotes from different installers and put them side by side to compare like for like – you can get info & quotes here: