Churchill, who changed parties twice, sat for no less than five constituencies.
I wonder why the UK is seemingly unique in having very little stigma against their politican carpetbagging.
I don't think this is true. Look at Canada.
The United States, as far as I can tell, is unusual in this regard. I can think of no other country with single-member districts where there is such a strong stigma against politicians contesting elections in a district that is not their home.
Honestly it's a rare good feature of American political culture imo. North Carolina actually requires members of the legislature of live in their district, which makes everyone quite locally attuned.