well good news, it appears if you download the .cfg file and edit the DNS Settings I can now use opendns!

So I simply went to backup settings on the netgear router, chose Save a Copy of Current Settings

Then I edited the .cfg file with wordpad, so it looked like this:

#< Domain Name Server (DNS) Address >
# 0ff 1n
[20601]"Use These DNS Servers"=1
[20602]"Primary DNS"=
[20603]"Secondary DNS"=

Saved it and then under the same menu on the router I chose Restore Saved Settings from a File, browsed to the edited file, and uploaded it

Not sure wether Sky can remotely wipe this setting or not?