A caxil of tweeters
A skulbuggery of hackers
A halfhead of hoodies
A sistitution of WAGs
A clart of environmentalists
A pig-pennorth of bankers
A whipple of MPs
A naysay of contrarians

I by no means suspect YOU of racism, Chris, but couldn't 'spic-and-span' be misconstrued in this context (especially in U.S.) - and so perhaps be ruled out as non-PC?
i.e. "a [hi]SP[an]IC-and-[hi]SPAN[ic] of charwomen"?

(I am only joking...)

Originally, I was going to go with "a wetback of charwomen." You saw through my sly effort to encode the racist epithet.

(As you probably know, "spic" in American English is probably the most offensive anti-Hispanic slur. I think it derives from the mocking phrase "no spic a de Inglish," but that could be bogus folk etymology. The most offensive anti-black slur is, of course, a Southern-accented corruption of the Spanish word for "black." The most offensive anti-Jewish slur, I understand, derives from kikel, the Yiddish word for circle. The story goes that Jewish immigrants to the US, asked at Ellis Island to sign with an X if they were illiterate or couldn't write the Latin alphabet, preferred to sign with an O rather than with a letter that resembles the Christian symbol of the cross.)

A tootle of tweeters;
A nerditude of hackers;
A hoodlummery of hoodies;
A catfight of WAGs;
A zealotry of environmentalists;
A backstabbery of bankers;
A blathering of MPs;
An apocalypse of contrarians...

I am particularly taken with a nerditude of hackers.

a trivia of tweeters
a cellphoney of hackers
a burberry of hoodies
a mall of WAGS
a warning of environmentalists
a sub-prime of bankers
a numbskullery of MPs
a contra-flow of contrarians

a chattering of tweeters
a violation of hackers
a surliness of hoodies
a handbag of WAGs (or maybe an orangery of WAGs?)
an earnestness of environmentalists
a bonus of bankers
an ineptitude of MPs
And I refuse to provide a noun for contrarians, because that's just how I am

ETA: Now revised to a "wittering of tweeters"

-I like it, Melanie!

1.
a gaffe of tweeters
a breach of hackers
a stereotype of hoodies
a ballpark of WAGs
an acclimatization of environmentalists
a winnowing of bankers
a margin of MPs
a fallout of contrarians


2.
a twitch of tweeters
a justification of hackers
an inroad of hoodies
a boutique of WAGs
a kendal-felicity of environmentalists *
a dolour of bankers
an interruption of MPs
a multiverse of contrarians

(* referring to Felicity Kendal's TV roles as eco-suburbanite Barbara Good in 'The Good Life' and as investigative horticulturalist Rosemary Boxer in 'Rosemary & Thyme.)