I had a Edwardian conservatory 2.5 meters x 3.5 meters build 2 years ago.
First I had a quote from a big company St Helens Glass
(which went out of business) about l year later.
The salesman spent about 2 hours just trying to sell me finance.
I went to two local conservatory small businesses for quotes. They were both excellent at designing what I wanted, and sorting out problems, such as moving my outside drain and having to move my boiler.
I chose one, and have been very pleased and satisfied with the standard of work. I paid �9,400. plus �400 to have my boiler moved, and an extra �300 because I wanted a radiator installed running off my central heating system.
He also included quality wooden flooring.
I dont know what part P is, but I contacted the Council myself to ask if I needed planning permission, I did need it.
This cost me �160.
I wouldnt go to the big companies. Go local. They should be FENSA registered.