The mystery of the "piano man" has been solved. This is the report in The Guardian.
Turns out it was a bit of a shaggy dog story. He's from Bavaria and the whole thing appears to have been an elaborate hoax. As for the 'piano genius' element - it does seem that that was the result of mental health workers in the UK not being able to tell the difference between a full-fledged concert pianist and someone who can just about pick out a tune from Swan Lake. The report on the TV news last night was gently accompanied by a background account of Chopsticks.