Regarding #4, this Allard was designed by Michael Eddowes, the lawyer involved in the Profumo Affair where he represented Christine Keeler. He also wrote several books including The Man on your Conscience, about the trial of Timothy Evans and John Christie and The Oswald File about the Kennedy assassination.
The coachbuilder of this car is unknown but may have been by a firm such as Fox & Nicholl who were responsible for some early Healeys, the aerodynamic HRG and a prototype Frazer Nash 420 open two-seater.
I haven't been able to find anything more positive at the moment.