Yes, this pointed me in the right direction, I just could'nt get the right combo of settings.
My file permissions are set as follows which just allows read permission for all other users.
Everyone now has read file permissions. The share then stipulates for a domain user in the write list
drwxrwsr-x+ 12 user share 4096 May 23 16:40 share
smb.conf
==============
[test-share]
path = /test-share
public = yes
read only = yes
browseable = yes
write list = +DOMAIN\WRITEGROUP
Thanks for your help, banging my head off the table a while back with this one.
Much appreciated.