Charley, as stated, Mrs Canatelli was written by Benny Gallagher & Graham Lyle. The recording I have is by Iain MacKintosh on his first solo album. The notes simply say:

[1974:] Benny told me they wrote this song about the landlady of their lodgings when they were in London with [their band] 'McGuinness Flint'. (Notes Iain MacKintosh, 'By Request')