Double glazing recs needed - West Kent

[PanicMode]

Can anyone help please? I am so fed up with the spivs who come in and try to sell us something for tens of thousands only to drop the price by over 50% "just for you", having banged on about their quality etc. If they have confidence in their product, why can't they just give a straight price?!

We have about 17 windows to do - we've had Anglian (no thank you), Everest (maybe, but expensive), Crystal (absolutely no way) and I don't know who to ask now. The quotes range from 15k to 3k! This isn't our forever house, but we're likely to be here for another 5 years or so, so want to get the benefits of good insulation, but don't necessarily need to go mega top end.

Can anyone help?!