OK, I'm new to this and I have probably missed something very obvious.

Anyway for trial purposes, I created a site, I uploaded a template, and I got phpBB installed.
Now I'm happy with the trial result I want to delete everything and start 'seriously'.

I can't find how you delete a database (entirely), and or delete the website in entirety.
(I can of course delete at file level using ftp, but I don't think I can use that to delete the whole site site or the database.)

Well, in your ZCP > Database Management, you should be able to delete the databases easily..
But for deleting your whole site you can't do this yet.

OK, thanks, and yes I had overlooked where the delete functions were located on ZHCP.
I've cleaned up ALMOST everything now, but there is still a small problem.
It's not database related, but I might as well continue in this thread.

The problem is that when I tried (using FTP) to delete the subdirectory into which I had originally uploaded phpBB, some of the sub-sub directories do not delete. All the files appear to have deleted. just not certain subdirectories.
I am getting the message that they cannot be deleted because they contain files, but no files are visible.

What ftp client are you using?

Some files are hidden - normally .htaccess or .htpasswd. If the ftp client does not see these, it won't delete them, thus the folders are not empty. There is normally an option somewhere to view hidden files.

swordz

Yep, there were hidden .htaccess files in those directories. (I'm using filezilla btw)