Thank you to everyone who took time to try the Alt+up/down arrow for me. It appears to be a bug, so I'll check Bugzilla.
I'll also amend the guide to point this out.
The Help files indicate it should be a working feature.
John
For anyone who may be interested.
The result of my search for this on Bugzilla reveals it was raised on the 11th July 2011 by Rainer Bielefeld. This was revealed in LibO 3.4.1. and has a status of 'Assigned'.
Unless I have misunderstood the comment that is on the report from the person I assume is the developer , then this behaviour is deliberate.
In order to adjust row height with the Alt+up/down arrow, you are required to change the setting in Tools > Options > LibO Calc - Compatibility, to 'OpenOffice.org legacy'. Not particularly practical.
Thanks again for input.
John
Oops. I meant to include the bug number: 39139