Don't think it's an M-type - maybe a sports-bodied Austin 7? Swallow Sidecars did some Austin 7 bodies, if I remember my early Bill Lyons history correctly.
My correspondent has immediately come back with 'late Singer Junior' suggesting a 1932 'Special Sports' style (though in truth, with perhaps a special body?) There is an M Type link, however, as the Junior used the same Rotax dash panel as the M type, so could see why you might have been confused...
It's a 1931 Singer Junior "Porlock". The 32 would have Magna wheels and a slightly different radiator. The 32, despite being called a Special Sports was a catalogued model, the special referring to the new 9hp engine.