When you "catch someone up" in AmE, it means you discuss what has been going on in your lives since the last time you met them.
catch up with - definition of catch up with by the Free Online Dictionary, Thesaurus and Encyclopedia.
See #4 under "catch up" here. "To bring (another) up to date; brief:"
I would use it as a verb, not as a noun.
Perhaps in BrE it has another meaning.