I suspect the answer to this may be "Take it to the dealer", and that's what I intend to do if I can't find the fault, however I'll ask the question:

Has anybody had an odd rattle from somewhere below and to the right of the drivers seat?

Mine started last week, it sounds like a screw/fixing rattling up and down and I get it braking down a hill and accelerating up one, as well as when I go round sharpish corners on the country road home.

I suspected the cavity under the plastic trim on the door so lifted it, but it's heavily insulated underneath and there's a large wiring loom that would block any objects rolling what sounds like a few inches.

It's also not in the door as I don't get it when I shake the door, ditto the drivers seat.

Is there a cavity under the drivers seat? (the sounds coming from inside the cabin so I assume it's not in the hollow sill)

Could something have rolled into the air-conditioning ducts under the drivers seat?

I don't want to take it to the garage and find I've dropped a pound down the seat!