After consideration I ended up buying another rear Q3.....thought process behind that was that it was the right price ($170 delivered), it meant I have a matching set and when it wears out the front will be toast too so I'll consider a different brand/compound then.
When I looked at the worn tyre I could see the tyre warmers had left their mark all around the tyre. Nice blue overheat lines exactly where the elements sit. After a little internet searching and reading Dunlops blurb etc I've come to the conclusion that the tyres could have overheated as I left the warmers on for a fair while in between sessions. The longest heat cycle coincided with my lairy rear let go in the second session with no real drama's the remainder of the day with the warmers on shorter cycles (apart from the nagging paranoia that the rear was going to let go at any minute lol). I'll post a photo of the tyre when I get a chance for anyone's feedback.
Next track day I'm going to shorten the length of time I have the warmers on for, in fact I may not even use them depending on the weather because these tyres do heat up super quickly anyway, I'll just take it easy for a lap (famous last words lol)