Bulk images from server

I am looking for a simple way to solve the following situation.

I’m making a website using wordpress for my photography club. The old site that is becoming redundant has a vast archive of photo’s which we obviously want to keep.

What would be the simplest way to import these images in the Media library so we can use them in posts and pages?
Is there a plugin which can do this?
The images are already on our server in several nested and/or different folders.

I tried the ‘Add from server’ plugin, but this gives me either an open base dir error on changing the settings back to normal, or says the root dir doesn’t have the correct permissions (all folders have 755 so I don’t understand this permission issue).