http://www.dvla.gov.uk/
"Service Unavailable".
Hmmm...
Ah. http://www.vehiclelicence.gov.uk/
*click* *click* *click*
Further ah: Since I needed the reference number from form V11 before I start the transaction, I've been to the intray and dug it out. Printed across the form in big letters, it says www.direct.gov.uk/taxdisc which then redirects to the second site above, modulo a skin.