You can get prices for supply off the internet- you just put the window size in and it calculates a price and delivery . Any handy man should fit them for around £15 each so that should give you an idea of what a blind company should be charging
I got vertical blinds twelve years ago from Hillarys Blinds from a shop in Seaview Road Wallasey, and have been pleased with them.They came out and measured. There is a website and apparently an up to 50% Sale: www.hillarys.co.uk/extra-10% Sale
I've been contemplating these for a while. Seen various quotes to have them fitted. The thought never occurred to me to source the materials over the internet. Ordered 2 blinds (via Ebay), one medium (ish) and one HUGE. Fitted them today. Piece of cake! About 30 mins. each one. Very pleased with the results! Thanks Fish for highlighting the DIY sketch.