that's the closest I can think of. If the style is more colloquial, sometimes the same concept is expressed by "con tanti saluti a..." or "alla faccia di", but "con buona pace di" is the most neutral choice, both in formal and informal contexts.

Maybe "con buona pace dell'attenersi ai fatti" if "buona pace dei fatti" sounds too strange.

Here is the entry from the Zanichelli Word on Words (dizionario di parole e frasi idiomatiche colloquiali e gergali):
so much for... (iron.) formula che dichiara l'impossibilità o la non verità della cosa che segue
- Oh well, sighed Alice. So much for a quiet evening. I've just seen Bob and Mary coming up the path.
Uffa, sospirò Alice. Addio serata tranquilla. Ho appena visto Bob e Mary sul vialetto.
- ... so much for being on my side.
Bel modo di stare dalla mia parte.

+++ However, depending on the context the phrase is in, it could also be used in the literal and non-ironic sense, and would mean "questo per quanto riguarda i fatti", before introducing something else. See for instance:

http://www.bootlegbooks.com/Reference/PhraseAndFable/data/95...
Dictionary of Phrase and Fable
Pendragon: A title conferred on several British chiefs in times of great danger, when they were invested with dictatorial power: thus Uter and Arthur were each appointed to the office to repel the Saxon invaders. Cassibelaun was pendragon when Julius Caesar invaded the island; and so on. The word pen is British for head, and dragon for leader, ruler, or chief. The word therefore means summus rex (chief of the kings).
***So much for fact***, and now...