I was served a PCN for parking in a suspended bay which happened about a month ago in Lambeth (London) Thornton Road R.
The only indication was the warning glued to the pink gate with plenty of other stickers, plaques etc around it. Other than that there were no markings all bay long (pun intended) which gives an impression that keeping cars off the bay is not their real intent, instead making an easy quid is.
I have challenged it and it was cancelled.

The reason I am writing this post is on multiple occasions I have seen plenty of other cars with the PCN on them in exactly the same spot. If you're an owner one of them and the bay looked like in the pictures which means it was not properly marked CHALLENGE! CHALLENGE! CHALLENGE! If they do not cancel it I am happy to support you with the response from the council, pictures, statement even going to court if need be.