I currently have a massive single paned window approx 3.5 m by 1 m in a brick built extension to my house. It is actually three windows, two small ones at each side of approx 0.5 m wide and a massive one in the middle.

As it makes the room quite cold and is a bit of a security risk, we want to update it to either a double glazed window or maybe even patio doors which would lead out to my garden.

Is there anyone out there that could answer me the following questions :

1) Do we need planning permissions or building warrants for any new windows or patio doors (the latter would require us to have 2 - 3 steps built outside as well)?

2) If we went for a window, I presume as the space is so big it would have to be along the lines of the current layout ie 2 small windows and one big one in the middle? Is this possible with double glazing? Most d-g windows I have seen are just one individual window.

3) How much would I expect to pay to have it replaced with d-g windows in this way?

4) Would getting patio doors be a much more expensive option (as there would be more building work to form the hole required fopr them and then fill in at the sides etc)?

Thanks for any advice - I know I should be getting a d-g salesman out to quote etc but I'm a bit wary of doing this before I have at least a wee bit of an idea what I want.

Thnaks again.