Well, to be brutally honest, I don't think your flight, in this particular case, would have been called a "weather diversion" under the Strasser scheme. I'm not sure what the exact criteria would be, but it sounds like you could just as easily have diverted to any other airfield in SE UK (and fuel permitting, outside of that area as well).
I realize that Farnborough would be ideal as it is close to your destination (Fairoaks) but "being close to your destination" should no longer be on your mind for a genuine all-charges-waived weather diversion, should it?