Mr Big wrote:
The added problem I have now discovered, is that right under the door,
is an airbrick.

So I suppose I cannot use anything solid and permanent as the step.

The step used to be an open wooden pair of steps, but they have rotted
and were always a pain in freezing weather and slippy. Any ideas of
how to make a wooden tread non slippy ??
you could build in brick and put a vent either side of the step to allow
air flow, maybe?