I would not charge as much as £220, but I would not supply a valve for no more than it cost me. Some valves cost me £58 + VAT , (Some makes are cheaper, but they may not always fit the system). I am not going to obtain a valve and supply it for the same as I paid for it. Shops buy something and sell at at twice what they paid for it. They have to, or go out of business (and even then some do). Unfortunately the firm is unlikely to have done anything illegal, if they have, speak to the Trading Standards Office.
How soon did they get round to fix the problem? Jobs can be done cheaper if you are prepared to wait, but if you want it done the same day it will cost more.
Why did YOU not fix your next door neighbours valve?
I have a valve to replace this week, job will be around £150, I also had a valve to sort, where nothing needed replacing, cost less than £50 to free the valve. Same day service, 1/2 hr travel and an hour to diagnose and sort it, (and it was a Saturday).
You will find someone works for years, and the prices don't change much as the years go on, as he's paid for what he wants and then it's just maintenance income. Someone else starts, and they have to get enough to stay in business their costs are different, and who is going to look after them when they can no longer earn?