Failed with lowercase, trying uppercase.  Noticed the host had a different secondary DNS to the installer so that has been changed to match.  All DNS servers have the correct forward and reverse entries.  The 172 and 192 DNS always had the correct entries but the 10 DNS that was secondary on the host didn't.  I've rebooted the host and rechecked everything to make sure settings are applied.  Time is synchronised on host and server that installer runs from.  Running again now but it's late over here so I'll check in the morning.  I'll let you know the outcome.  Thanks