Can't do links on the phone, but Tunnie your advice is wrong, pure and simple.
Granted the charges are unenforceable but it is the responsibility of the registered keeper to demonstrate beyond reasonable doubt that certain conditions have been met. It is impossible in 99% of cases for the companies concerned to meet those conditions, but since the law change ignoring the notices is not an option.
Google parking charge notice and read all the advice given on the site I suggested...
For an educated person you can be quite daft sometimes 
Well loads of people from the office must be wrong too
we've all ignored them and get nothing. 
But that doesn't mean you give out wrong advice based on a tiny sample of evidence. The actual rules re: private car parks are exactly as Al described. The car park you mention may not have an interest in pursuing the issued tickets, but your statement re: binning the ticket could potentially get someone else into a lot of trouble.
Just as you say, the speed limit on the M'way is 70, people do 90, but if someone does 90 at your advice and gets caught and loses their licence, then your personal experience of not getting caught so far doesnt mean anything to the person standing in front of a judge.