I'm going from memory here but I believe the footwell lights lie horizontal.
So if you plug a normal w5w led light in you will just be shining most of the light on to the end of the lights enclosure.
So you are looking for led's that are along the bulbs side as opposed to just the end in order for more light to be thrown out.
I'm sure someone will be along soon if I'm talking nonsense

Similar to this:
