I took mine to Nationwide Autocentre a month or so back for a full aircon service and regas.
I had problems with the car and needed Audi to have a look and at the same time the aircon wasn't working and they wanted around 100 quid to regas.
So I took it to Nationwide instead who were doing full service and regas for £69. After about an hour and a half of waiting, I got told they couldn't regas it and so I was expecting a bill. However, they said they wouldn't charge me and off I went.
Have no clue on how Kwik Fit works though so I can't comment on them.