It's part of a weekend being run by the guys from Llandegla for SheCyclers - see the thread here... Hopefully the link will work!
As the instructors from the centre are guiding, there is a charge but I think they've negotiated access with a landower for a ride towards Llangollen so it'll be somewhere we're not usually allowed to ride (don't quote me on that but it is something that Llandegla were talking about arranging).