It doesn't seem that pronounced or serious but I have noticed a bit of gear whine in my fabia VRS at low speeds, revs particularly in fourth and third when you change down.

The change is still smooth and the synchros don't feel as if they are going and the dealer has told me not to worry about it. I don't abuse the box but I just wondered whether "they all do that" or whether trouble may be brewing. MY old Fiat Uno( many year ago) box used to whine, the garage said "they all do that" but it eventually blew its bearings and I had to have it reconditioned.

Any ideas?

Try a search; there's pots of good stuff on whining gearboxes including replacement under warranty. I, for one, benefited that way.