B
breezer
if you want to cut out a hole for downlights you could always use this which means no mess on the floor below, or you could use this but you have dust on the floor.
Either way, once you have made your holes* in the ceiling you can "fish" from one to the other, so you may not have to lift any floorboards at all. (mind you lucky if you don't since one joist will always be where yo do not want it)
* you can check where the joists are by hitting the ceiling as mentioned in a previous post, or poke a very small screwdriver up to find them, but best lift a board to be sure
Either way, once you have made your holes* in the ceiling you can "fish" from one to the other, so you may not have to lift any floorboards at all. (mind you lucky if you don't since one joist will always be where yo do not want it)
* you can check where the joists are by hitting the ceiling as mentioned in a previous post, or poke a very small screwdriver up to find them, but best lift a board to be sure