I sent Airfix a request online as my cambelt on my Internal Combustion Engine model had broken. Not only did they send me one free of charge, I received it the next day. Amazing customer service!
I agree, many years ago as a little lad I got a kit that had a few parts damaged on a sprue. I wrote a letter explaining the problem, and I think two days later I got a whole sprue of parts sent as a replacement.