Yes, I know of Gyrus. In fact, much of my reference probably comes form his work on the Goddess of Wharfedale - which is a very good piece of detective work. I've not read Julian Cope's account - but I'd guess his references are the same as mine.... perceptive lad that Gyrus!
Yes a gaelic 'v' is a stange phenomena - mh can also be pronounced as 'v' and as 'w'... and can also be silent.