Hi MarcJ
All I can say is that it took me a while to get either a SD or HD signal delivered through HDMI to my Philips 32" LCD via the TV Drive. I had to choose HD (720P) swtich the TV to the HDMI input manually, then press ok on the TVDrive remote to test the signal. Initially I just got a blank screen, then after a few days I got a terrible broken/scrambled pcture with the TV showing that the incoming signal was swapping between HD 720P and SVGA. It took a week of telephone calls to Telewest to admit there may be a problem with the TV drive (although they were very helpful on the phone) but, last night, it suddenly corrected itself and now shows a superb picture, I still don't know what changed.
You could try setting your LCD to HDMI input then change the resolution of the TVDrive on the front panel rather than via the remote.
To do this, press Reset on the TV Drive, then hold down play and stop together until "boot" appears in the display. Release the play/stop buttons and wait for OUTPT to show in the TV drive display, then press the FF button until HD... is shown in the display, then press OK. After another 30 seconds or so the signal should change to HD assuming you have selected HDMI rather than component in the Telewest settings screen.
Good luck!!