Come on chaps let's not fall out with each other, sharing is power!.
It was about two years ago when I was getting the letters I even posted on here somewhere a picture of the parking ticket on my windscreen :) But I was under the impression that it was only UKPC car parks that could take you to court and make the fine stick all others are just chancers, hoping you will pay by scaring you with letters, regardless of contact or not. I'd just assume they would harass more with contact mainly because you have replied and they will try up the scare procedure . I've thrown my ticket away now and the letters I think will dig them out if I have them, I'll have a look tomorrow.