Steve,
Thank you for your advice - I had asked so many people and never got a straight answer.
Have to say that Weathershield's blurb is not the clearest - if I wasn't quite so '*****' I might have just gone and painted 'breathable' waethershield on top of the limewash. . . glad I checked ('measure twice, cut once').
Looks like I'm in for a learning curve this summer

Excellent site mate, cheers!