I got mine from www.klarwindows.co.uk
No issues with minimum orders and cheap if not free delivery.
I couldn’t find anyone to install them so am doing it myself with help.
15 windows and 1 front door and 1 set of french doors came to £11k, about 33sqm. I’ve gone for triple glazed aluclad. Some of them have been in a year and I’m pleased so far.
They often have sales which are genuine, eg. Black Friday was a genuine discount. The website will always say 40% off which is the discount compared to velfac etc. Sometimes the discount for patio doors goes up to 65% off.
Happy to explain a bit more about installation but it takes about 4 days work per window taking into account the removal of plaster, making an airtight connection to the house and then insulating the reveals.
Just a note that they are very heavy - 30kg per sqm. Our front door weighed over 70kg and even the lightest window was 40kg.