Measure in from the access hatch below and then from above.
Failing that, small masonry drill bit. It'll go through the plaster of the ceiling but not, the wooden joist. Try and repeat, until you hit something. Note, the ceiling pendant will likely be attached to a joist and then, 400mm (?) intervals away from this is a good starter.
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