Yes, they are paired.
I didn't want to just add/subtract what I already have, but get hold a complete set if possible. I've looked at the Campag spares, and yes, there are some missing from my list! Perhaps I want something that doesn't exist in the stock range.
By changing to 12, 13, 14, 15, 16, 18, 20, 22, 25, 29 I would get even steps - or as even as possible.
The option of going to 11sp would be better than going compact. That way, I could get a 12-29 in 11 cogs, but it's a very expensive way: Cassette, Chain, RH Ergo. Other than that, Compact is another way, as you rightly suggest, but that's another expensive conversion: Chainset and Bottom Bracket and a Cassette. Also Compact wouldn't give me the range, as I'm Chorus Triple 53/42/30.
My idea - providing I could get the cogs, is a simple and least cost way.
Do any other manufacturers make Campag compatible 10sp cogs?