This is turning into a short course for networking - but here goes. ;)
Network comes before Applications - especially on Internet servers. In order for Moodle to function to the global internet it must be connected to a TCP/IP network that allows access to port 80 (the port Apache serves Moodle from/out of). The Moodle server must also have a fully qualified domain name (FQDN) assigned to it from DNS servers ... both internal DNS servers and the external DNS servers. One cannot just make up what looks to be a valid FQDN and configure a Moodle server to use it. A DNS server administrator MUST enter the FQDN and associate that FQDN with an IP address.
The dig www.diabetes.cmdn.dundee.ac.uk output shows NO answer. Therefore, the DNS server to which Moodle was talking (SERVER: 10.1.255.216) doesn't have records for that FQDN www.diabetes.cmdn.dundee.ac.uk. Also, that FQDN has NOT been entered into ANY DNS server that folks (like myself) would query to FIND your Moodle server - ie, outside the private network DNS servers.
So who ever is the DNS server administrator(s) no entry in DNS has been made for the FQDN you are trying to use for your server: www.diabetes.cmdn.dundee.ac.uk
And, the cmdn.dundee.ac.uk boundary firewall may NOT be allowing port 80 traffic to the server. We can only check things from the server perspective. It would seem to me that the IT department should help you enough to get the server on the network so that it could be accessed. Hmmmm ... have heard those things before ... 'ok on our end', but turned out they didn't do what was required. Sometimes one has to prove it to them by testing from your server ... ie, inside out.
Ok, when logged on via ssh and as root user, type:
/sbin/ifconfig [ENTER]
We are looking at the NIC - and the ports where the wires plug into the server.
In the output one will see a line with:
inet addr: .... and an IP address.
If it is configured for connection to a private network the IP address will be one of the following 'ranges':
10.x.x.x - 10.x.x.x, 172.16.0.0 - 172.31.255.255, or 192.168.0.0 - 192.168.255.255
Your server probably should be in the 10. range judging from the DNS server that your server attempted to query when you tried to look up your servers host name (fully qualified domain name): 10.1.255.216
That IP address you've been using while INSIDE the private network: 134.26.65.163 probably won't work while you are on the INSIDE the private network.
So try going to the IP address you see in the output of the ifconfig command above while you are INSIDE the private network.
Also, from the command line let's see if the Moodle servers firewall is allowing port 80 traffic. Again from ssh session as root user:
fgrep "dport 80" /etc/sysconfig/iptables
In the output of that, one should see something like:
-A RH-Firewall-1-INPUT -p tcp -m tcp -m state --dport 80 --state NEW -j ACCEPT
And one more thing before we close this 'lesson' ...
from the server again, let's see if it can talk to the outside network:
dig sos.tcea.org
You should see an IP address in the ;; ANSWER SECTION:
ping -c 5 [thatIPaddressseen].
BTW, some networks may not allow workstations/servers to use ping so one could also try that curl command:
curl -I http://[thatIPaddressseen].
If things check out on your server ... and Apache/Moodle are setup to respond appropriately, then there is still the issue of DNS. Here again, DNS server administrators must make entries in both internal and external DNS for Moodle to be able to function by 'name' ... ie, http://www.diabetes.cmdn.dundee.ac.uk
'spirit of sharing', Ken