I'd suggest you have a conventional 19th Century conservative-reactionary grouping; a sort of liberal group (bit more nebulous, but would ideally fit either the UK or France depending on if the concept was economic or social) and a revolutionary left grouping. I'm not convinced that fascism as such calls for such a model - too nationalistic at the end of the day.
As grossly inaccurate as it is, it could take over the reactionary mantle late in the game. Absolutism was no longer a vital force, and fascism did at least have in common its rejection of the values of the French Revolution. Plus it segues nicely into the Axis.
'Course there's no credible left defender for most of the period either.
I'd say the IRL liberal defender would be Britain throughout. I figure America wouldn't take over until during WW2 - high isolationism should make it hard or impossible to claim such a title. France meanwhile just didn't have Britain's reach, never mind the Third Empire joyride.
The reactionary / fascist defender would beyond doubt be Austria until, say, 1866, Prussia / Germany thereafter, and then after the war Italy (if Italy can be called a GP) with Germany taking over right at the end.