It's been debunked numerous times in the last twenty years, yet every now and then, raises it's head.
Yes, the Hitlers did briefly live on Upper Stanhope Street (L8) prior to WW1, but it was his cousin or brother or something.
There's no proof what so ever that Adolf himself came to stay, although that doesn't stop the rumour mill giving it a kick every now and then.
On the dates that he was reportedly in the city, there is documentary evidence (in the form of official paperwork) that he had to report to a police station or some other government official in Germany/Austria, because he'd previously been arrested or some other such thing.
I can't be arsed trying to dig up the source right now, but I might try later.