I think it's really pot luck on this one. I've had good and bad experiences with both kwik-fit and local independents. Last independent I tried charged me for new valves but actually took the old valves off my old tyres and put them on my new tyres. One of these valves failed a week later, I popped into my local kwik-fit and asked them to have a look. They spotted the ancient valves on the new tyres, put new valves on and charged me nothing at all, as they said they did not have a price code for new values only on their till. They simply suggested I put a donation of my choice in their charity box which I was happy to do