I don't know anyone who's had new windows recently to recommend a company. So I suppose I just have to get the yellow pages out and ring around. But you hear such horror stories of dodgey window firms, so is there anything I should avoid or questions to ask?
I guess you don't have the option of asking around for recommendations?
We had ours done many years ago with BAC (now SEHBAC) and the product was (and still is) very good, but the aftercare is complete rubbish. We had someone try to break in a few years ago and damaged part of the window, several years £700 and many many phone calls later it is still not fixed. Also have a problem with some hinges (just need to buy some specific new ones), but they are not the least bit interested in returning my calls.
I would not recommend them.
I have however learnt that there are only a few companies that actually make the windows and doors - most companies that sell and fit windows just buy them in from these factories. Not sure how that will help you. I guess I would ask lots of questions about the aftercare and ask for some references.