Hi Tony,
I am basically just following my old basing convention for 28mm figures which was derived from the old WRG 1685 - 1845 rule set. Rather simplistic but lots of fun back in the day, but my intent is to use my contemporary figures alongside my older ones. Given that I will be able to field both sides the basing doesn't really matter for most modern rule-sets, and I have always preferred the shoulder-to-shoulder look of four figures on a 60mm x 20mm base. Mind you, most of the older rule-sets were developed at a time when Hinchliffe were the largest figures around, so at times it can be a little cramped.
The group I game with plays mainly 15mm with a rather intricate set of home-grown rules, where the basing is more along the Empire lines. The British and Portuguese are the only ones that are defined as being two rank from memory, so they are based in a more extended order (3 figures to a base, with each 12mm x 12mm) than all other armies (3, 4 or 5 figures to a base depending upon nationality, with each 9mm x 15mm), but utilising a more effective firing table than the others. This feels more realistic to me, but makes them completely rule-dependent.
I debated whether I should paint up these 28mm regiments as single units with both standards on the command base, as they were always brigaded together anyway, but I preferred the flexibility of keeping them in their separate battalions so they could operate in concert but also independently if need be. There are undoubtedly too many figures in each when compared with some of the other armies I am putting together, but I figured that it is always easier to take a few figures away rather than leaving oneself short.
That's just my rather muddled thinking and, in my case, it has mainly come down to the group I game with. That said, I'd probably just base them the way you are intending to base your British.