Don't you just hate it when you spend ages writing a detailed review [twenty minutes in this case] and it doesn't go up?
Since my review of this contained information on how to find a couple of easter eggs on the dvds I'll mention them here instead:
on disc two of the silurians don't use play all to watch the episodes, go to select episode instead. if you do, then after the end credits of episode 7 you will find an original bbc trailer for the ambassadors of death, the story that came right after this one in broadcast order. you can get this to come up by fast forwarding through the episode, by the way, you don't have to watch it alll the way through to make this appear.
On warriors of the deep: if watching on a pc go to the second page of special features, and move the pointer over the screen. you should light up a hidden doctor logo in the middle left of the screen as a result. click on this and it'll play a four minute long feature showing the models used in the story. it's worth watching.
if watching on a dvd player go to that screen, move the pointer down the middle, then press on left, and it should play