You would be better off discussing that matter with you local bulding control officer (BCO) - this work would come under Part P of the building regulations.
You are allowed to do the work yourself but must pay the fee to have BCO come and check and test your work and issue the appropriate certificate.
Alternatively and probably cheaper if you employ and an electrician who is a member of a competent persons scheme.
When you consult BCO you might like to think where your appliances are; how you want them lit; what type of lamp you will have in your downlights; what wattage lamp you will have. The BCo may have an answer. If you can tell you local electrician what you want then he/she will know the answer. It's between one and ten.
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