If you should discover, while sitting in a airport departure lounge, that your TomTom has lost its SD card, don't despair. Provided you have a spare SD card (I stole the one from my camera) and have the laptop you've used TomTom Home with to hand, all might not be lost. I was able to do something along the lines of:

cd /media/disk
cabextract ~noodles/TomTom/HOME/Downloads/navcore_7.131.8483.one.cab
mkdir "US - Western Region"
cd US\ -\ Western\ Region/
cabextract ~noodles/TomTom/HOME/Downloads/US_-_Western_Region.cab 
umount /media/disk

which got me up and running again. Of course it doesn't have the UK maps that came with the device, but as I was on my way to the US that's not so important (and Katherine has found the SD card anyway, so I can just replace it when I return). I was quite pleased with myself. And then I ended up with a rental car that had GPS of its own anyway...

(Oh, yes, I'm in Fremont, CA, flying back on the morning of Saturday 18th November. I am currently jetlagged and trying hard not to go to bed. If you are in the area, know me and would like to meet up for food/beer/whatever feel free to drop me an email.)