This could get complicated to try to explain over the net and will need a little more info, first of all will need to know are the two lights supposed to come on together from what you say I assume they are. The black cables are all neutrals except one of them and that is the one that goes to the switch and must be connected to the brown of the flex going to the lamp sometimes this black wire has a bit of red tape or red sleeving over it.If as I assume both lights come on together then you will have to identifie the wires that go to the landing light as they are connected slightly different to the rest of them. I assume the wiring is twin and earth and not single cables (twin and earth is enclosed in a white or grey pvc sheaving.
If you give us a bit more info then will try to help you out further......