The challenge is to keep at least Scotland and Ireland seperate and independant from England. How could such a thing come about? Bonus points for Welsh independance as well.
My personal suggestion is have the English Civil War be a less clear cut affair, but more geographically divisive, heavily weakening England before eventually dividing it into two states: The Puritan English Commonwealth and the Kingdom of England. During the chaos you could have Irish and Scottish rebellions that gain outside support, cementing them as independant. The Welsh could rebel too but I doubt they could succeed. Any other suggestions? Comments?