Do some more digging.....
If I were looking I'd get a quote from
First 2 that caught me eye.
Ask for local references. Speak to them and get a feel for them on a personal scale, anything that is a "familly run business" and has been established for 10 or more years has to be worth checking out..
Albion, to me look like a company set up by an ex employee of one of the nationals who know what they'd quote and have gone a shade under. Might even have a source feeding them quotes for back handers as it's so close to the original.
Re-read the advice from others here. We have absolutely nothing to gain so why would the majority be in agreement?
Enough from me. I self-fitted my 6 windows as I'm incredibly finikity (and they were all ground level and no existing windows to remove) and saved myself £500 for a weekends work plus I know they're fitted superbly. ;)