Well, Rowan, you'll be happy to know that I use a professional editor. She is very affordable, and she is very, very tough in her assessment, which is just what I want.
Truth is, an agent doesn't have time to edit. She likes your manuscript, or not. "Editors" at big publishing houses, ditto. Their job is to purchase new stuff, and the title "editor" is just a remnant of times long gone, like the vestigial tails of tadpoles.

The people who do edit are line-editors. That comes very late in the process, or not at all. I am currently reading "The Hemingses of Monticello" which is a GREAT book, but unfortunately not line-edited. The difference really shows.
So will I go on using my own editor? Oh sure.