Sharon Osbourne -- Curbside Singer Hits Her with Abba ... Gets Cash and a Dream

Sharon Osbourne got a guy's number last night -- a guy who belted out a song for her in London ... and who also happens to possibly be homeless.

Osbourne was leaving a restaurant when she was serenaded by a dapper looking guy -- who photogs claim is homeless. The two swayed back and forth while he sang ABBA’s “I Have a Dream” ... sour notes included.

Osbourne handed him a few British pounds (about $80) -- and we're told she even said she’d give his number to Simon Cowell ... for consideration on one of his TV shows

Britain's got talent -- and some of its homeless people apparently have phones.