Nothing aperently!
When the technition took it out initially he could not fault the car, and was actually quite complimentary about its condition generally.
I took him out and demonstrated the noise which he could clearly hear, he felt it could be any component in the transmission with a little bit of play in it, just suggested I drive a bit more gently and go back if it deteriorates.
So happy no imediate spend required but I am pretty convinced that if I drove another car it would not make the same noise.