Sorry, for the delay in replying, and many thanks to those who did.

On Tue, 30 Oct 2018 at 19:08, Scott Kitterman <debian@kitterman.com> wrote:

Did you explicitly remove Apparmor? It's shipped by default in Ubuntu and the
Ubuntu clamav has an Apparmor profile included.

That was exactly it! I was unaware of Apparmor now coming enabled by default. It's the first time it's ever caused me any issues.

For anyone looking for a fix in the future, do the following:
1. Uncomment the local config include at the bottom of "/etc/apparmor.d/usr.sbin.clamd"

2. Add the system paths clamd should have access to in "/etc/apparmor.d/local/usr.sbin.clamd"

3. Reload the apparmor service

Many thanks for your help all!

Doug