It's oddly specific mockery, like Ozzy is England's international representative. I don't know, maybe he is. But I doubt Birmingham even inspired the meme, this is probably a caricature of Dick Van Dyke more than anyone.
To be fair, Brits seem to think New Yorkers go "oi" and they don't really either.
Anyway London accents don't go "oi". This is a Birmingham accent. London accents go "ah".