Oh, just discovered another bug.
If I turn the subtitles on for any channel using the Subtitles button on the remote, as soon as I change to another one or go to EPG/other menu there is a thin vertical line of graphical trash (i.e stray pixels) on the right hand side. This persists across channels. This is only visible when the HDMI setting on the TV is set to Screen Fit, i.e. 0% overscan, so it occurs to me this bug wasn't discovered because whoever codes/tests the firmware had their TVs overscanned at least slightly. It disappears only when the unit is hard rebooted, i.e. switched off via the back panel not standby with the remote. Simply turning off the subtitles doesn't banish it.
Here's a few pictures of my 32" Samsung LCD TV demonstrating the bug.
<cheesy> Just call me Zeke Pliskin, Unpaid Virgin Media Field Tester™. </cheesy>