I was reading wikipedia on Great Britain because I wanted to see If i can dig up some not so contemporary looking flag

And then I noticed this:
So basicly that's why It doesn't feel right when I see GB form in 1400s. Because in my games so far it did that and which was worse Kingdom of England pops up as independent and they coexist (even if the english form GB).
I never played England/Scotland so I have no idea what are the requirements to form Great Britain and also am by no means a specialist in british history.. but! Shouldn't the forming be more difficult and require more than just conquering territories?
I'm pretty sure that the English wouldn't change the whole name and everything if they conquered scotland in the 1400s. I believe they would just try to suppress them and still call themselves kingdom of England. Just bigger and more glorious.
How about making it more historical? Read this:
http://en.wikipedia.org/wiki/Acts_of_Union_1707
Based on it we could have the "pass the act of union" decision with the requirement to be X years into personal union with Scotland/England. Good relations, maybe good prestige and low Infamy. Just an example.
Actually looking at this article about all the different attempts we could have a few situations which would allow you to form it depending on the circumstances. Would feel less straightforward and historical at least in my mind.
Ok rant's over I wanted to get this off my chest