don't know why I didn't think of this before... telnet. (possibly because I've never used it before!)
I've written an applescript which will telnet in to the nas box and send the commands to shut it down. I also added a little question first just incase someone runs it by mistake. Ideally I want to add this to the the shutdown sequence, but I've no idea how that works!
here's the code just in case someone else is after it.
Code:
set question to display dialog "Hi There. Matt's iMac here, are you sure you want to shut down the NASlite Server?
(PLEASE press NO if you've no idea what this means)" buttons {"Yes", "No"} default button 2
set answer to button returned of question
if answer is equal to "Yes" then
tell application "Terminal" to do script "telnet 192.168.xxx.xxx
admin
password
8
Y"
end if
works like a charm!