Charlie, I think you got it right. I checked on various websites and the climber seems to be what you said it was. I do remember picking up a papery seed pod while out walking along one of Madeira's levadas. Thank you lots for identifying it. What a pity it's a weed though. I will wait for the flower to appear before deciding what to do with it but it looks like it will be a trip to the compost heap for it.