yes, there's one for each episode. (i love the behind the scenes stuff).
they're usually almost as long as a doctor
who episode. you can find info about them
on the bbc doctor who website under the "confidential" link. (i guess i can't
post links here.)
i think the confidential stuff ends up as extras on the dvds too.
i have no clue about ponkers and plonkers but maybe the above poster was
referring to the use of 'there'...should be 'they're', 'they're all around 350'
because spell check won't help you with a mistake like that.