Hi Ed,
Yes, it's a Dell Special.
However, after a bit of searcing on here I found this:
http://www.mp3car.com/vbulletin/show...ht=sx260+sx270
I'm using a DSX12VD PSU and have wired it up to the battery through a 30A relay with a switch on the dash. I could have gone for a DSX12V instead as I've not used any of the timer or other "Deluxe" stuff but our UK supplier didn't have them listed.
I cut the Dell cable off of the PSU brick and resoldered it onto the molex connector.
Red and Brown went to +12V.
White and Black went to Gnd.
Yellow and Green were taped off.
Then put the new connector into the Dell and Bob's your Uncle.
One bonus is that I can now use the old Dell PSU as an indoor 12V supply.
I always use Hibernate when exiting for a nice quick bootup. The Dell is set up to boot when power is resumed, so when I make the switch, power comes on and the PC resumes from hibernate.
And so I don't forget to switch off the PSU, I also wired in a lights reminder alarm so if the PSU is still on when the ignition is switched off a buzzer sounds.