Charlie Brown was probably a main factor in rehabilitating the name; he's well loved this side of the pond. With his shy, diffident nature he seems quite British

.
Also, British people love Charlie Watts! What's not to like? So he's more likely on the side of rehabilitating the name than the cause of using it as an insult.
Note, I'm only suggesting that 'Charlie' has (had?) insulting connotations in the UK, so pointing to Charlie Wilson of General Motors and Rep. Charlie Wilson is only making my case. Where are their British equivalents?
Charles Darwin: (i) He was never called Charlie (ii) The "Right Charlie" insult didn't come into play before 1930 (if the Cockney rhyming slang idea is correct...)
Charles De Gaulle is fine 'cause he's French.
http://en.wikipedia.org/wiki/Charles is fun, it appears Charles' in Britain could have no luck:
"The original Anglo-Saxon was Ċearl or Ċeorl, as the name of king Cearl of Mercia, that disappeared after the Norman conquest of England."
"The name's etymology is a Common Germanic noun *karlaz meaning "free man", which survives in English as churl [A rough, surly, ill-bred person; a boor; A selfish miser; an illiberal person; a niggard.]"
"Charles, Prince of Wales, would become Charles III ... but he has reportedly considered choosing George VII as his regnal name" [Not such a Charlie then!

]
Oh well, Charles Dickens and Charles Darwin have done a lot to save the name from total disgrace in the UK!