Judging by the pictures and recipes, it looks delicious. I doubt I can get the correct Arnott's biscuits anywhere nearer than London, but I imagine it will be fun trying British alternatives
Any biscuit that looks like the top right one here should be perfect:
Really, any crumbly biscuit that turns "cakey" when wet would work.
Really I'm not sure why Arnotts haven't extended over there, I feel like Ripple biscuits and tim tams would be big hits in other countries.
Sure, Australia has it's problems but to me I feel like we have the best junk food. Well, I guess that may not be considered a plus.