Hi Charlotte Golledge - that is an amazing piece of information!
If you read through the messages (most from me!!) you will find one from Bob Sharples, a son of Rab, who was an original Inverscotia.
He and his brother may be able to give you more detailed info than I can?
Also worth checking out Seylan Baxter / her study of the Inverscotias,:

(Scottish Republican and Socialist Movement: Hillwalkers, Long Distance Melodeon Players and Gangrels)

My pal the songwriter Iain Ingram has inherited the role of organiser of The Tryst, a follow on from the Inverscotias' annual spree.
I'll try and make him sign onto Mudcat - but as he may never get around it I'll try to liaise--- do you have a work email address? or are you on facebook?
If not, can you join mudcat then we can message each other privately? (I don't actually think the whole world is sitting poised, ready to leap on my personal details but - just in case?!