The loom, like all options on the RRC is a stand-alone item, so no it is not already fitted.
That said wiring them up isn't difficult, especially if you dispense with all the interlocking to stop you moving them unless thew ignition is on OR the driver's door open :roll: .
I did it with mine anyway. The bit you need to get in good working order is the switches, these are worth more then the seats (unless they are dark brown or black). If you don't get them I can give you a wiring diagram to get them working.