Richard,

https://cycle.travel/gpx/831622.gpx

I plotted this route on ct. All was fine until between mile 28 and 29. The ct route that I was following was  not possible at this point because at the route turnoff to the north it had been designated ( correctly or incorrectly ) ‘Private’ and was gated. Is this a mapping change or a Landowner ‘at it’? Unfortunately the re-route  options for getting to Cairnryan are not then  great from a safety point of view ( since Stena moved their port from Stranraer to Cairnryan ), as cyclists have to use a v busy ‘A’  road with a poor and limited cycle path. I can provide photo’s of the ‘Private’ Entrance if that helps .

Thanks 

John Buswell