C Glass Vs K Glass in Patio Doors?

[BonzoDooDah]

We need new sliding doors into the garden (glazing blown, old aluminium frames, wooden frame rotten) and have had a few quotes for direct replacements. Two quotes say K Glass and are about £1500 the other says C Glass and is about £1000.
The cheaper C-glass person was recommended by a neighbour who's had doors done by them 5 years ago and more windows since and has no complaints. In fact highly recommended.

The other two companies are reputable, with good reviews.

So it comes down to the glass. Can anyone tell me the real difference between c and K glass and if it is "£500 worth of difference" on a set of floor to ceiling doors?

Thanks!

is this : pilkington K glass? I am trying to find info on Solar control glass and pilkington comes up on other threads about conservatories and folding/sliding doors in extensions as a reputable company. I typed C glass into google and didn't get much! I think you should ask the people who gave you the qoute what the difference is - it might help you. If they are very informative then you'll get a feel if they are being honest or just fobbing you off and if they can't give you a satisfactory answer then I would get out of there!!!

Yes that's the K glass I mean - will ask the C glass supplier - but I'm tending to agree that we should go for K and A rating with big windows.