I would like to change the dns servers used by my 2860n
On the LAN general settings page I can see the primary and secondary DNS settings to change. On the 2820 series there is an option to force DNS manual but not on 2860? Is the another setting I need to change in my 2860 to enable the force DNS manual option?

Force router to use "DNS server IP address" settings specified in LAN X :?: (half way down LAN General Setup page)

Thanks, so is it just a case of inputting desired DNS server IPs in the details page for say LAN1 and ensuring that the forced lan box is ticked for Lan 1 , no need to change anything in the advanced settings box ?

Yes if that's all you want to do. Why not try it and see if it does what you want? I use Google's DNS on mine.

Thanks Piste,
I also normally use Google 8.8.8.8 and 8.8.4.4 but the reason for change was that I want to hide my IP and browse anonymously. I have an account with Hide My IP which I use at the browser (I.E.) quite successfully. I wanted to set up the router to ensure that all devices in my household were anonymous.Their help and support suggests that changing my DNS settings to two of their servers will achieve this. However it doesn't do this and with the new DNSs in place my public IP remains the same. I'll revert to them to ask more questions. I had always assumed I'd have to tunnel from my modem to one of their servers but thought I'd try this first. Any steers or views on this subject would be welcome.

As I understand it using a different "smart" DNS server can't/won't change your public IP, it will just route traffic as if you were in a different geographical location.