Mr McGrath of Harlow I read some facinating stuff about St Ninian (of Dumfries and Galloway fame) who setup a pilgrims route (the date escapes me but around 600 AD seems to ring bells). He travelled throughout Europe but established a route across the English (or possibly Scots then) mainland right into Ireland via Galloway paticularly the Isle of Whithorn (which isn't an Isle but a peninsular).

This became a kind of pilgrim and trade route bringing all the benefits of cross culture from Europe , mainland England / Scotland into Ireland and therefore BACK again. He became quite a famous person in his day. I capitalise BACK because with this route established as early as this date the intercouse in music and other culture like art and craft would have been arterial and duplex. This would make the determination of which belonged to who(m) difficult if not impossible from the resulting homogenous creation.

It could explain , in a little way , the noticable similarities in the North East English / South West Scots and Irish music and instruments in particular and then again reflected into European music in general.

Well....It facinated me....

Spot.