At the last house I finally got fed up faffing around getting boards up - and I treated myself to a nail puller. It's like a slide hammer, with jaws on the end. Jaws open either side of a nail, hammer down till the jaws have sunk far enough into the wood, then lever over and the jaws grip the nail head and pull it out. Leaves a rectangular indentation, but the least damaging technique I've found. I pulled all the nails in one room and put screws in - no sqeaksThe nearest I have to that is some Victorian T&G floorboards, which I am reticent to damage more than I have to.
There isn't on our extension. The original house is the style where the walls are lower than theupstairs ceilings which slope down with the roof line for the last foot or so. The extension (teed off the back) has the same roof profile, but instead of a regular ceilng, the lounge has a vaulted ceiling - so no attic at all. There's a spot right at the apex of the gable where I could drill through from the outside and fish a wire alongside the ridge beam - but otherwise I'd come through into the lounge.However, since the OP was talking about "...a few lights on the outside gable of the house", I had though that they could probably potential access from roof space - although maybe there isn't access to that, either!