Your best bet is to check the hall light fitting for an unswitched(permanent) live and take a cable from there to a new switch and from there to the outside light.
Okay, what do you want to know exactly?
You will require a permanent live, a neutral and CPC/earth conductors.
Don't be fooled in to thinking that all black or/and blue conductors are neutrals!
You will often find on switching arrangements that the blacks and blues are switch lives.
There are number of differing lighting circuit arrangements:
*some loop in both permanent live and neutral at the ceiling fitting.
*some loop in both at the switch.
*some loop in live at switch and neutral at ceiling.
If you need to find a tradesperson to get your job done, please try our local search below,
or if you are doing it yourself you can find suppliers local to you.
Select the supplier or trade you require, enter your location to begin your search.
Please select a service and enter a location to continue...
Are you a trade or supplier? You can create your listing free at DIYnot Local