I can't remember having to remove the manifold from my R1090 Dauphine in order to remove the starter motor. As John says, it's just a case of disconnecting the electrical leads, then removing the two starter motor retaining bolts using a socket on a long extension. There's enough room to wiggle the starter motor out. John's 4CV has different manifolding from my R1090 and yours is different again. Yours would have the same manifolds as a Dauphine Gordini which probably would make the exercise even easier.
Yes, we'd love to have you in the Renault Car Club of Queensland. RCCQ conducts lots of interesting events and there are a number of people who could give you valuable advice. You can make contact through our website. If you have any trouble with that, please let me know how to get in touch with you.
I have removed/refitted the starter on a Dauphine Gordini (same engine/gearbox as Floride) without removing the manifolding. I can remember it being a little awkward given the work area, but OK. My hands are not small, and no doubt I had to squeeze them in to get the job done. From what I remember the terminal connections were the most difficult part of the job.
It is worth checking the voltage at the main terminal (voltage drop) whilst starting to determine whether the battery or terminals are the problem of poor starter operation.