Quick summary of my changes, for reference:
I've removed meta description. Some of my descriptions made no sense (a by-product of trying to create useful summary content from UGC content). So, rather than attempt to create something I can't be proud of or confident in - I've removed them.
I've disavowed most of my referring links that had low cardinality. Ie, one site linking to my homepage a thousand times etc.
Meta de-indexed (MDEd) all tag pages
MDEd all second pages of 'threads results' (list of threads, not actual content)
MDEd all search results (i had mostly done all that before, but tidied it up)
MDEd all image pages (even though some had 100k views)
MDEd all profile/user pages.
Other minor bits and pieces.