Getting a wire from the passenger compartment to the engine compartment.

I want to fix a second cigarette lighter socket in my Peugeot 207 (2009). The existing socket turns off when the ignition is turned off. This fine for my navigator and the odd top-up for my mobile phone. I need to use my laptop for work (not while I’m driving!) and I’d like to charge it while I’m driving and let it continue to charge when I park. I’ve bought a new cigarette lighter socket and I’ve fixed it in a panel in the passenger foot well. Wiring the earth connection is easy but the live isn’t. My laptop needs about 8 amps at 12 volts (I can buy a converter to match this to supply needed for the laptop). I can’t find any accessible wires near to the fuse box to piggy-back a connection because everything is wired to tightly. I think that my best bet is to run a wire (protected by an in-line fuse) directly to the battery. My problem is getting a wire from the passenger compartment in to the engine compartment. I could drill a hole and protect the wire with a grommet but I can’t find anywhere accessible. Does anyone have any ideas where I might drill (without hitting a servo or other vital part!) or whether there is an existing, accessible place?