Could be a number of things really.....thrust bearing for the whirring, gear linkage for the hard gear change, cable seized for the hard clutch....definitely something I would have to get checked again. Maybe go to a decent specialist if you can find one near you rather than a dealer....a "diagnostics" on something mechanical like that is not going to show the problem and needs to be driven and demonstrated. Find a specialist (you are in London, so there should be a few around) and take it there. I am sure they will give you a definitive diagnosis. Unless its driven, not sure anyone, unless they have had the same problem, will be able to say anything different or definitive. Hope this helps?