Just realised mate mine is in the recess behind the n/s lights not the wheel arch. It should have a 12v cap/cover on it if it's there. Not sure where to wire it up if you haven't got one. Might be worth speaking to an auto electrician, but at a guessI'd say straight to battery with fuse/resistor inline. As the cig lighters are a constant live in a Seat
I'm pretty sure they wernt fitted to all models. It may be worth getting behind the lining in the area mentioned above as I wouldnt have thought the looms would be different. If so there may be wiring there for it.
If not as dav says wire back to battery or spare way at the fuse box with suitably sized cable and fuse.
the power outlet in the boot wasnt in all leons. it was in early models, then it wasnt, then it came back,then went
fairly easy to do, run a power cable off of a source (battery direct maybe?) use 10g as a guess. have a 10amp fuse in line and connect to a cigarette lighter available from most places and connect the negative to a good earth source.
do it that way and it will stay on with ignition off