Here's what I hear:
dah T dah dah dah O di dah di dit L dah dah dah O di dah dit R dah di dah dit C dah dah dit G di dah dit? RSo, it appears that the message begins: "TO LORC GR". I assume that is meant to be "TO LORD GRANTHAM" and that the C is actually D and has been incorrectly transcribed.
Here's the audio as an MP3: Downton Abbey Series 1 Episode 1 Morse Code (first part).
Then over loud music it continues:
dah dit N dah dah dit G dit E di dah dit R di dah di dit L di dit I di di dit S dah T di dah A di dah A di dah A di dah dah dah J di dah AI think that's a fragment of "NGER LIST AAA JA". Since AAA is a full stop and this telegram is referring to the sinking of the RMS Titanic where Patrick and James Crawley were on the passenger list (as we later learn in the episode) it's likely that this is a fragment of "PASSENGER LIST. JAMES".
Here's the audio as an MP3: Downton Abbey Series 1 Episode 1 Morse Code (over music).
Anyone else hear something different?
PS It's pleasing that the producers must have gone to the trouble of composing the complete telegram and the recording its transmission using Morse code just for that small segment at the beginning of the first episode.
PPS A little Google search reveals that it was G3YXZ [PDF] who was recruited to send the CW and he notes that for television reasons the key was adjusted to increase the gap size thus making sending more difficult (hence, no doubt, the mistake with C and D).