Well, I'd call that a green light then.

As a matter of canon, Shyri's plotline mostly stuck within Britain itself, so really the only sticking point is the South African invasion. But even that, aside from a few dialogue bits among the rest of us, hasn't entered the general story yet. 

So I'd say, pending Googer and Aaron's opinions, that you can do pretty much whatever with Britain so long as it makes sense. Only rule is the general "WW1 sucked and Britain wasn't geopolitically relevant for a while" rule that we tend to apply to most European countries so as to keep things consistent.