Having been variously gold, bronze and silver over the last 5 years: I place the value of silver very high, and the relative value difference between gold and silver being only slight .
To me, the biggest and most important difference is the first wing. If you travel from LHR a lot, and it sounds like you do, that's a perk that makes entering that specific airport much nicer .
For the rest of the world, I don't perceive a sufficient value difference, except perhaps extremely superficially.
As others have pointed out, you can have more avoid redemption opportunities with Gold, but that's not something I have needed in the past.