I may be wrong, but as far as I can make out, the requirements of Part L regarding lighting only apply to new builds or if there is a "change of use" - so I don't think that a rewire (or even major renovation of the building which did not involve a change of use) would invoke these requirements.I cannot remember is Part L applies to new builds or rewires. If this is the case for a rewire then ...
Kind Regards, John
It includes rewiring of lighting circuits, reasonable provision should be made to obtain the benefits of efficient lighting.
Section 1 43