Hi nice to meet you all. 

Im hoping to start a display cake business up in the UK as shabby chic is quite popular here.

Ive watched videos on your tube of people using various bases like foam, cardboard, Polystyrene and then using a filler or plaster as icing BUT im guessing filler and plaster would be toxic so i was hoping someone would know what i could use instead to cover the faux cake and then what i could use as the piped on icing that is non toxic please? Thank you 

Buttercream, I do all my displays in buttercream and then when I want to change the dummy cake I just scrape off the buttercream ,wash in hot water then dry  and the dummy is ready to use again.

Well, filler and plaster aren't toxic or they'd never be used on walls, etc. as there'd be a lot of dead contractors and homeowners......

I take it that you're worried about yourself using the products, since the final creation would be dried and not eaten?

You can cover & decorate dummies with buttercream--the cheap kind made of nothing but powdered sugar, vegetable shortening, and a bit of water.  You can also use royal icing with a bit of glycerine added to it so that it has a longer working time.  You can use rolled fondant and decorate with royal.  Honestly, all are cheaper than plaster/filler, but will fade faster.