PCC,
I have all of my relays mounted on these blocks
http://www.narva.com.au/Switches_19.html
When you need to change them you just unplug them, they can also clip together so that you can keep all relays in one spot. I have a panel with all relays circuit breakers in the kick panel on the passenger side (thanks Mando), with undoing 2 screws the panel is removed and all components are there.
Phil