I did find a forum post that helped, it was to do with the 'path to - log & tmp' address.
forum.joomla.org/viewtopic.php?f=471&...=0&sk=t&sd=a
I tried different configurations until i got the write one, needless to say it was different than expected!
/home/xxx/xxx/
The JMS update then installed absolutly fine....
However I got back into the office today and the 'Path to Folder' address has reset itself to localhost/xxx/xxx/
This means that symbolic links were again forbidden - so i changed the address back again and seems ok.
Why would this address change, both;
- Server Settings > Path to Temp-folder
- System Settings > Path to Log folder
Strange?!?!?!