Thank you for the further advice, I really appreciate your interest.
The person on Genes who I am corresponding with, and for whom I've created an Ancestry tree, is not comfortable with digital issues (it's become apparent).
Although I've now sent him an Ancestry invitation and a web link to the tree (new facility from Ancestry, a one-use weblink) on two occasions, he's been unable to access the tree.
He says he is waiting for a visit from his more technically capable daughter and son-in-law, which may be delayed given current circs.
So I'm rather unwilling to take the time to explore other avenues of exporting the tree to Genes Reunited in case he's not able to access it there either......
It's been made apparent to me exactly how handicapped people are who've not had the opportunity of developing computer skills (perhaps at work), so as to be confident of what they're doing.