I built a bumper for my 1999 disco II; you can see a pic of it on this link
http://www.oausa.net/forums/viewtopic.php?f=32&t=916
and this second link is the credit for the plan and design. I did a few things different but pretty close.
http://www.pbase.com/robv/2007_disco_bumper
I hooked up mine using the factory fog light switch. My understanding is that switch is on a relay. I have two Hella 4000s on it for a few years now and it works fine.
you can check out these sites
http://www.hicountryoffroad.com/Products/Discovery/Bumpers/discovery_i_and_ii_rear_bumpers.htm
http://www.trekoutfitters.com/discovery/index.htm
http://www.rovertym.com/
I have the Roof Rack it is a custom made, modeled after the Safty Devices rack. Made by a local shop here in SO. Cal. I am still looking for some good cases to hold gear and supplies.