You still need to get an IFR approval for these VFR-only planes, as I see it.
Unless you plan to do loads of illegal VFR, but even then you have the airspace classes against you; can't fly where you can't get a clearance, and I would expect VFR clearances through CAS are not trivial down there (same as here).
The actual flight is trivial, with a GPS.
Range-wise, a TB20, with a massive ferry tank, could do 2500nm which means 2 fuel stops from London to Cape Town, and that is without even exceeding MTOW. If you go to MTOW+30% then you could do it with 1 fuel stop. Interesting toilet arrangements.... better start off with an enema, and not eat any veg for the preceeding week
IMHO the record will always be held by narrow-cockpit planes, for speed / fuel flow reasons.