The artist in the vid says the foam is used for large scale props and he has not seen it used for something that scale. I think if it was floral foam he'd says "it's the stuff they use for floral arrangements"
Extruded polystyrene, or XPS, is easily obtained in the US (and I assume other countries) as sheets of home insulation at local home improvement stores.
most model metal casting is whitemetal...its soft and melts at a low temp. It wont give you a clink though. Casting steel is going to be harder because of the temp involved
I have NO symapthy for R2/Autoworld on this. They created the 1701 club...that wanted those 1701 sales right off the bat (plus Standard kit and accessory packs) They had the same 2 years to figure out how the heck to bill and ship the product.
They fell flat on their faces plain and simple...