The gardener in this house, (not me), is trying to get hold of ribes
(rubus?) benenden. Having failed with all her usual local suppliers, she
is now casting her net wider. Does anyone know of a possible source
within 15 miles or so of Coventry, or a possible on-line source?

I'm supprised that no one has given you the correct name for the plant
you are looking for.
Its Rubus (tridel) Benenden
http://www.shootgardening.co.uk/plant/rubus-benenden
I've grown it for years, will get rather stragly if left alone, but
well worth growing.
David