Question for Al (or other British posters)

[Filuwaúrdjan]

The quick answer is that in the 19th century only the right-wing of the Liberals were called Whigs; the "left" of the party were usually described as Radicals (and some had never had anything to do with the pre-1832 Whigs at all).
Most of the higher-profile Whigs (remember both the Liberals and Conservatives were top-down parties), eventually, found their way over to the Tories (often via the Liberal Unionists (a party that broke away from the Liberals over Gladstone's policies on Ireland) which was, ironically, led by Joe Chamberlain, who was very much a Radical), meaning that the name was, basically, dead by the early 20th century.

As a side note, what was left of the old Radical wing of the Liberal party (although they'd obviously ceased to use the name) was wiped out in the early 1950's. Most of them later joined Labour (Megan Lloyd George is the best known example, but there are others).