Many thanks for all the latest replies.

I've been trying to find the exact building regulation governing step access
to outward-opening garden doors but for some reason I can't now track it
down. Google searches seem to throw up a bewildering array of possibilities
none of which address this particular point (or if they do, the info is so
well-buried as to be for all intents and purposes invisible).

If anyone can point me towards a straightforward explanation of the
situation and what needs to be done, I'd be very grateful. Thanks.