Hi, I have just installed a Vigor 120 to increase the speed of the internet as we now have 2 broadband services. Is the load balancing automatic or to get the best out of the 2830n do I need to make some setting changes??

look at the load balance policy page.

You can set some address to use which WAN you want..

So for example 1 set a download server to use WAN2 while my desktops use WAN1

for best results i'd give all your device static ( bind ) IP's on the Drayteks DHCP , so you can group different type of devices to each group of ip's
for example all Wireless access points, network printers , cameras to 192168.1.10 - 192.168.1.20
Servers , and main desktops 192.168.1.2 - 192.168.1.9