I see what you mean better now Rob.
I think perhaps a p seal might help BnQ do one dunno if the dimensions would work but look at it.
I think perhaps a strip just where the inner door curves down might be a good spot, and take it down the sides about 150mm
Thanks for the suggestions.
I had thought of ordering from Sealsdirect
(their P42 Rubber P-section).
But I'll have a look at B&Q first - their website shows a couple of draught seals which may work.
Your suggestion to add another strip on the inner door curve is also a good one. Thanks!
I'll report back once I've fitted something.