I've replaced all the interiors bulbs with Phillips LED bulbs and it works fine.

The only problem is that when the front centre dome and back centre dome is on the 'auto' mode (lights on when doors open), the LED bulbs are dimly on. When in the off mode, 100% off.

This must mean there is a small amount of current running when on auto mode.

Is this normal? Can I do something about it?

I imagine it is only noticeable now since LEDs can show some light on very low currents where as on normal bulbs it would show nothing.

Is this going to run the batteries flat?

Ran ross-tech as well, no errors.