Have been out of gaming for some time and so not sure about this:

When using a headset - can you blank out all audio coming from the TV set? Ie get audio only in the headset. I'm thinking of getting the Sony one if it works that way, as it would allow me to game more comfortably in the presence of others :)

Also, is the Sony headset the best available or would you recommend others?

I don't have the official PS3 headset myself, but I've heard a number of people say that it's really good.
On the other hand, it's rather expensive - and since it's just a standard Bluetooth headsets like hundreds of others on the market, I guess you can buy one with equal or even better quality for less money. My Bluetooth headset for example cost just a third of the official headset and I've never had the slightest complaint.

By the way, if you don't mind having a wired headset, there is a really cheap alternative:
http://www.dealextreme.com/details.dx/sku.22475
For just $ 2.23 including shipping, and you can use any standard PC headset/headphones with your PS3.

So can you shut down tv sound through the headset?

Can anyone answer this?

Pls help!

What system? PS3 or 360? Why is it in gaming discussion????????

PS3 :)

if you want all sound that comes out of the tv then no the official sony headset can't do that you only hear the voices.

Is there an alternative to go for - suggestions on brands, etc.?

as far as i know its not possible