Getting double glazing - what to ask/check/look out for

[maswera]

I'm getting double glazing and deciding between a few quotes. As well as a good price price I want to make sure I get a company that will provide a good guarantee, won't go out of business in 2 months (or if they do, the guarantee is still valid), won't damage the walls, etc... Has anyone got any advice on what I need to make sure I ask the companies to make sure they aren't cowboys and will resolve any problems that come up?!

TIA

They need to be members of either certass or the cpa who will underwrite their guarantees.
Avoid Safestyle in my opinion and Everest as they use hard sell tactics.