Image button (and others) not showing in Redactor toolbar

(Searching the forum this seems a common issue, but I've not solved this yet.)

I have the following in my redactor settings:

redactor:
  -
    name: Standard
    settings:
      buttons:
        - formatting
        - bold
        - italic
        - unorderedlist
        - orderedlist
        - image
        - file
        - video
        - table
        - link
        - html
      formatting:
        - p
        - h2
        - h3
        - blockquote
        - code

And the following in my fieldset:

            fields:
              block_content:
                restrict_assets: false
                type: redactor
                display: Content
                image_dir: /assets/uploads/
                file_dir: /assets/file/

(The asset directories are there too)

The image, file, video and table buttons still don't appear. Any ideas what else I need to do?