Thank you all, for the considered and helpful advice. I've been a member of this forum since 2002 and it's never let me down
I can't get any of the suggested options to work fully. I think I will either install Parallels to allow access to my 2610, or try and pick up a mega cheap laptop running Windows. Either way, having gone onto the GARMIN site, I don't fancy upgrading to a new GPS unit. The 2610 is an ace bit of kit and I just don't see the point in trashing it. I'm only interested in old B and unclassified roads, after all.
Thanks again.