HTC is on a roll for Gingerbread updates today. First the HTC Desire got the Gingerbread treatment with a non-tradition RUU download. And now the HTC Desire Z is seeing Gingerbread in the form of a more traditional over-the-air update. Android 2.3.3 will be pushing out to unbranded Desire Z handsets in the UK across all networks starting today.
If you have a network branded Desire Z, you may have to rely on your carrier to push out the specific update for you phone. Which might just take a little bit longer for them to get around to doing. You may want to ask your carrier about the update.