Agreed that Alan Sugar’s grammar is atrocious, however he speaks like a bit of a geezer, and it’s a regional dialect thing. He probably knows it’s grammatically incorrect and doesn’t care, and I bet if he was writing he’d say ‘you were’ not ‘you was’.
When the candidates say ‘myself and Ryan were in charge of that’ or ‘I really want to impress yourself, lord sugar’, they are deliberately changing ‘I’ or ‘me’ or ‘you’ because they think it sounds better. IT DOESN’T.