[Closed] Double glazing dilemma - Anglian, Everest or local guys?

We want to take out an existing wide window in the kitchen and remove the wall and put in full height French doors leading directly onto the garden. So far had both Anglian and Everest round and the quotes are £500 apart around the £3k mark. For doors about 6ft wide and 7 ft high including removing the retaining wall, latest thermal glass, British Standard locks etc.
Both firms have forums full of horror stories but in the face of it the have 15 guarantees etc. Should I get a local person in? How will they compare? They offer 'insurance backed' 10 year guarantees only? Or should I get a builder in and buy the doors online?
Your advice please. Live in Wokingham area