Multiple installs and secret keys

WordPress MU would be much easier to manage

There is also a plugin called wp-hive
https://www.ads-software.com/extend/plugins/wp-hive/
that will let you do a WP-MU like thing in regular WP without needing to learn WPMU. However, any admin on any one of the hive blogs has access to every one of the blogs. If you completely trust everyone who will use one of the blogs, the hive approach will work well. Otherwise WPMU is more appropriate.

Is it ok to use the same set of secret keys (required since wp 2.6) or will these need changing too.

that is ok to do

Incidently, if I want to do 20-30 installs, would members recommend using WordPress or WordPress MU (I’m unlikely wo want to upgrade installations as this is a short term project).

Mu is good but you should really have some experience with installs, servers, etc.
Of course, it’s easy enough to download it and give it a whirl.

review this, also
https://me.mywebsight.ws/2006/08/11/host-multiple-wp-sites-on-one-installation/

Thanks folks. I’ve had a look at the Hive approach but it doesn’t say whether it is compatible with WordPress 2.7 and it doesn’t appear to allow subdirectory installs at the moment (only subdomain).

I presume this method: https://me.mywebsight.ws/2006/08/11/host-multiple-wp-sites-on-one-installation/ will also require me to set up subdomains?

I’ve had a quick go with WPMU but haven’t quite got it right yet but will persevere! At least I can fall back on single WordPress installs if if only have to change the table prefixes.