Right I think i've narrowed down what's happening, thankyou for your suggestion about the usernames. After renaming the user account on the laptop, it's sort of half using it. The user has been renamed, but when accessing the network it still uses its old name!
I experimented with the default account on one of the laptops:
On the master pc is an admin called Cloud
On the slave laptop pc is also an admin called Cloud.
I renamed Cloud to LaptopTest and rebooted, but when accessing the master pc, it still has the same permissions as Cloud. Any permissions i set for Cloud specifically, the laptop ends up using still. However if i create a brand new user account on the laptop, it accesses the master pc using that specific user accounts name. So i had to delete my RenderSlave user (which previously had a different name), and remake it for the change to actually take effect. Now when I'm setting permissions for the RenderSlave user it's actually working :D
Edited by draqen4, 14 October 2017 - 12:45 AM.