The first half of the mould hardened up nicely overnight, so it was removed from it's Lego frame and the plasticine carefully taken off.
The other half of the pouring funnel was added with plasticine and the Lego frame rebuilt. The mould was coated in a thin layer of vaseline to stop the two halves of the mould becoming one solid block of rubber and then the top half was mixed and poured on.
This has now been set aside to harden, it should be ready to open in a couple of days but I won't cast from it for a week to ensure the rubber is fully cured.
My only point of worry is that the figures look a little too much like Nazi penguins at the moment...