I sympathise, Yorkie!
One way to get your own back when you see one coming, is to deploy the 'anti-chuggers emplacement'.
This means that when you see the offender, (silly little chugger, prancing around showing some sort of clipboard), turn away with a mobile phone in your hand, and pretend to chat. Make sure you're in their way, and they have to stop! Take no notice of them while they struggle past, place mobile back in pocket and walk on - usually with a small smile...
Works every time!