I know how to move hosts as i've done it more than once my question is:
i'm building my board up on a new host adding a few new plugins as well but if i was to import my other db from a backup to my new host would i just be able to activate the plugins as normal to update the db or would i need to add the plugins to the old board as well.
You could just disable them all before you switch, copy the files over, edit the files to fix with the new database and domain, and then re enable your plugins. I am 99.9% sure about this as i did it before like this and it worked.
yes, as matt g suggested, disable all the plugins, if possible uninstall them as if you are ready to loose settings which gives more accurate installation of settings on new host. upload the already installed old plugin files to your new host and install them and then restore database. later add your new additional plugins.
I've already got the files on the new host i used a backup of my files, i've added the new plugins and activated them to make sure they work on the new host.
The only thing i'll move from the old host is the database as everything else is already there.
The new plugins won't be recognised in the old db so i'm hoping they will be listed as deactivated then i can activate and set them up as normal.
yeah, unless you activate the new plugins after copying the plugin files, you can activate them later.