Assuming the UK adopted the EASA definition of cross country flight, then:
Cross-country means a flight between a point of departure and a point of arrival following a pre-planned route, using standard navigation procedures.
so probably not a 15nm jaunt to an exercise area, at least not for the full hour. Only relevant if you're hour building for the CPL MPL or ATPL, of course.
Personally, I would try to keep everything in one logbook but with separate P/UT totals, much easier done electronically. As far as the CAA are concerned, all PIC time is loggable irrespective of where it was flown and what the registration was, so counts towards the revalidation requirements. P/UT time in Canada would not, so hours with a Canadian instructor would not count towards CAA licence revalidation. No doubt Transport Canada has similar requirements. If it's all too complicated keep separate logbooks but include overseas PIC time in the CAA logbook and, if allowed/relevant, UK PIC time in the Canadian logbook.