I recently watched the one set on the holiday planet with a deadly surface...

Q: What Midnight?

The one with the avaricious lizards using human skin suits to disguise themselves as politicians.

Q: What Aliens Of London?

The one where the Doctor gets aged by hundreds of years.

Q : What Last Of The Time Lords?

The one where the villain duplicates himself thousands of times over with a device designed to heal an entire planet.

Q : What The End Of Time?

The one where K9 blows himself up.

Q: School Reunion?

The one where the villain is rejuvenated to the point of infancy?

Q: Boom Town?

A: No The Leisure Hive.