Thanks for that interesting link Tim.
I knew it was originally a fox-hunting call, but I have always preferred the phrase's aviation connections. (And many early aviators were horsemen, as you know.) And FYI I used to be an air traffic controller - but never heard "tallyho" used as described (except in fun) perhaps that is another British-ism too.
Years ago I dated a girl who was of the "horsey" set and a bit snooty. There was much discussion within the "hunt" group about who was sufficiently proper to invite to a hunt. After weeks of observation of me, and exchanges among themselves, she and her friends grudgingly decided I might be barely suitable, and I was invited to join a local hunt.
I intentionally showed up in a western saddle, cowboy hat and boots, with a rifle scabbard alongside (complete with a 357 Mag Rossi 92) and asked "Where's the fox?" - they were not amused - and further invitations were not forthcoming!
I might point out as background info, that the relationship between us was pretty tattered by this time (for many reasons) and it ended shortly thereafter. I like to think my "hunt" had much to do with the break-up.
By the way, there were few foxes in that location, so they decided they'd enlist coyotes as their subjects. I figured a 357 Mag Rossi would do nicely under the circumstances. Unfortunately, no coyotes applied for the postition that day.
Cheers
Kerry