I justfound a local nursery that stocks Mrs RB there were only 2 possibles within 150 miles of here and fortunately the nearest - 15 mile trip - had one!! So now I shall see what she does here.
Of course I came back with two others as well - Clematis Wyevale - a tubulosa in rich blue and heavily scented and Clematis Recta Peveril, a mounding white clem, also scented. All 3 are midsummer to autumn flowering when blues and whites are in short supply in the garden.
We already have several spring flowerers so once I get these new ones are sorted I shall have to acquire one or two of the spectacular large flowered showy climbers like Nellie Moser and the President but I'll have to build an arch first. - and dig up some more lawn