Until September 20th, you can get 20% off items purchased on the BigW ebay store, using the discount code PBIGW. It says that there are T&Cs, but it isn't obvious where they are (if online at all), but does note that there is a maximum discount of $1000.

They don't have a lot of Transformers items listed, and of the toys, most are "random assortment", as they only list size classes instead of individual toys.