Thought a bit of an update was due. 5 months later and I'm no further forward. After in excess of 15 phone calls, all following the same, "I'll have to contact so and so..." line there's no word of a replacement after being promised one months ago. It would be safe to assume they have no intention of sending one.
On a side note, while I recognise this could've happened to any piston, it's a bit disappointing that it happened after less than 5 hours and then to be faced with absolutely dismal customer service. A friend of mine had the same issue with a PROX piston. They replaced the piston and replated the cylinder FOC! Also, I recently had a PROX valve spring break on one of their steel inlet valve kits shortly after being put in. I rang Prox about the problem, sent back the old spring and valve and they sent out a new kit the next day, as well as giving me a half price piston. That, in my opinion, is how customer service should be. Suffice to say I will never entertain a Wossner product again...