Red White Yellow and Black streamers and bunting won't inspire today's Britons to much patriotic feeling, and could scare old folks into thinking the country had been invaded. Maybe as time goes by things could change.
One immediate effect though -- Jamaican-Britons would be pleased to see some of their ancestral colors worked into Britain's new flag.
Any of those would be fine in my view, except the third one - and that’s only because it violates English rules of Heraldry, which their flag really should follow (and which are why the white is retained around the cross of St George in the Union Flag).