I currently have 1 adsl line with O2 as ISP using a 2820, no problems there.
I will soon need to have a very resilient situation for email collection and sending and incoming web access.
My idea was to get another line in with a different ISP, set up another 2820 with Load balancing and a 3g usb modem should the copper down the street get cut.

Will this work?

If I have a fixed IP on router 1 and that isp or phone line goes down surely that means that that IP will not be visible from 'outside', or will router 2 automatically route requests to that IP address to router 1?

How will this work if there is no copper, will the 3g modem automatically connect and allow outside users to connect the same way?

Thanks for any help