The group is reenacting a bout from 1860, just prior to the American Civil War. The girls in the "American" boxer's group are carrying modern 50-star US flags.
When Libby Morris talks about going to 'the U S of A' she mentions Moose Jaw, Wyoming. The city of Moose Jaw is located in the Canadian province of Saskatchewan. There is no 'Moose Jaw, Wyoming'.
Just as Jones enters 'Midsomer Norton Turf Accountants', there is a spelling mistake on the poster in the window advertising the John Kinsella fight; Accountants is spelled Accounants.