Hang on a minute...

I've just realised, having looked more closely that, while connecting it straight to the battery is correct, you will need to cut of the white connector and connect one wire to an ignition switched feed to trigger the relay, and the other to earth. If you don't connect these two wires up there will be no power at the sockets!

This connection will only require a very low current so could be connected to the connector behind the dash that I mentioned earlier. You may have to extend the wires to reach it though. There are other places you can get an ignition switched feed under the seat, such as tapping into the tail/number plate light wire and then taking the earth direct to the battery.

Got you. So essentially solder live to tail light feed and solder the other wire to black neutral battery wire ??

Essentially yes. It'd probably be easier to use a Scotchlok to tap into the tail light feed though and i'd just fit a ring terminal to the negative and stick it straight on the battery.