I have commenced upgrading my 2830n to the latest firmware (3686 from 3685), and immediately on trying to "restore" receive the following dialog message: -
"Warning: Config filename mismatch, restore anymore ?"

What will happen if I say OK? Will it bork my router? If so, I may need to change this kit for something more reliable and up-to-date.

That is a re-importing the config file, rather than the firmware upgrade?

Might be better off running the .rst firmware and then re-configuring from ground up.

You shouldn't restore backups from different f/w versions.