Customise Read More ?

This will likely have to do with your theme and WordPress itself, not the FWP plugin.
https://codex.www.ads-software.com/Customizing_the_Read_More

Thanks for the reply but I have already a customised Read More link setup for my blog posts.
But the read more links for the imported posts have a different link and code.

I haven’t seen that. Could it be the feed is pulling that in and you’d need to strip it out with some custom code?

You maybe right. I can’t find a setting for it. Hopefully someone can come up with a solution.

Thanks