So I finally got the time when my mum was not using the web to flash DG834GT_V1.03.22_DGTeam_1018_eng_adsldrv023o.img using nftp.
First time it hung half way through verifying which scared the hell outta me, but I just hit ctrl+c then ran the same nftp command again which flashed successfully.
When it booted back up I was not at all surprised to find that the web interface still was disabled, doh. So I took the time to do some digging this time and as I suspected it must be an issue with the configuration as mini_httpd was NOT running.
I did a little more digging to see how the router boots and discovered how to temporarily turn the web interface back on. Simply telnet in and run "/usr/sbin/rc httpd start".
However I think there is still something wrong with my router or the 1018 firmware, because most of the Advanced pages come up blank as does the Access Mode page where I would turn the web interface back on permanently.
I guess the next thing is to try restoring factory settings. Fortunately the Backup page IS working so I have at least been able to do a backup of the current configuration so have nothing to lose now.