Does this even apply to a 750 Breva?
It applied to my 2004 Breva 750. I posted a rather detailed description of how to do this without the kit (which is a more elegant and neater solution, eliminating all the fun of wiring, fusing, soldering, crimping, and such).
It is my contention that this is actually a problem that has the potential to affect any MG from the last 50 years, since they all ran the starter voltage on tiny wires up through the switch. Consistency is the hobgoblin of small minds, as Oscar said (misquoting Johnson).
The relay involved is usually (but not always) the second one on the right frame side on most small-blocks of the modern era. It can be easily identified by placing a finger on each relay in turn as you briefly attempt to start the engine. You can feel it trip.