Ok to help others, I found the answer very shortly after posting this.
In the theme settings, there is a section called typography. Now I previously ignored this as it didn’t seem to change my blog post text format.
The reason for this is that the imported text from Blogger, as part of the import file, seems to have some kind of fixed text (in this case, Arial).
I’m not sure how to change all my old posts (65 posts) to the standard font, but I’ll be looking into that next.
If anyone has any ideas on that last part – I’d love to hear your suggestions.
Thanks