Hi @philipstorey,
After reading my last post, I can see how it sounds like I was saying you could customize how the meta title is set. Apologies for that; the meta title is set to the blog post title, and that functionality cannot be changed. I meant that the blog post title is changed from the settings tab.
What you might consider doing it customizing your blog template using HubL to create a ‘public’ blog post title that is used for your actual blog post titles. You can then use the default title field for SEO purposes. It might look something like this:
{% text "blog_display_title" label='Set a unique post display title', export_to_template_context = True %}
{% if not content.widgets.blog_display_title.body.value %}
<h1><a href="{{ content.absolute_url }}" id="hubspot-name" class="link hubspot-editable" data-hubspot-form-id="name" data-hubspot-name="Blog Title">{{ content.name }}</a></h1>
{% else %}
<h1><a href="{{ content.absolute_url }}">{{ content.widgets.blog_display_title.body.value }}</a></h1>
{% endif %}