I didn't think this was supported on any networks in the UK but my W850i on Vodafone just came up with:

15-Dec-08
21:10
GMT
Accept Update?

I think it might be only Vodafone that support it actually...

I've had the same thing happen on Orange when the clocks change

I didn't think it was done through the network. I know the iPhone uses the time server thing they use on their computers, plus the phone should be smart enough to know about DST settings considering phones and computers are pretty much the same thing these days.