The final for this cache can be found by looking up the episode number (single digits only, the right most digit in the case of numbers over nine) in which the quote appeared.
N ab° cd.efg
W hi° jk.lmn
[a] The Doctor: "Nine hundred years of time and space and I've never been slapped by someone's mother."
[b] The Doctor: "And with that sentence you just lost the right to even talk to me. Now back off!"
[c] Dickens: "How exactly are you a fan? In what way do you resemble a means of keeping oneself cool?"
[d] The Doctor: "I might never make sense again. I might have two heads. Or no head. Imagine me with no head! And don't say that's an improvement. But it's a bit dodgy, this process. You never know what you're going to end up with."
[e] Jackie: "Gherkins! Yeah, pickled onions! Pickled eggs!"
[f] Cassandra: "It depends on your definition of people. And that's enough of a technicality to keep your lawyers dizzy for centuries."
[g] The Doctor: "Oh, never underestimate plumbing. Plumbing's very important."
[h] The Doctor: "Time's been damaged and they've come to sterilize the wound. By consuming everything inside."
[i] Gwyneth: "I swear it is the strangest thing, Miss. You've got the clothes and the breeding but you talk like some sort of wild thing."
[j] Rose: "Doesn't the universe implode or something if you dance?"
[k] Pete: "Blimey, you know how to flatter a bloke."
[l] The Doctor: "I've waited a long time to say this. Jackie Tyler, do as I say. Go and check the doors."
[m] Rose: "You can't let them run around inside dead people."
[n] The Editor: "Yeah, well, simply being human doesn't pay very well."
Thanks to debaere for beta testing this puzzle.