What repairs do you have to carry out on a regulated tenancy property

General Discussion

I have a flat with a regulated tenant in it. the maintenance of the exterior is the responsibility of the leaseholder.
Recently her heaters which had been wired in failed. Who pays to have them replaced?

Another problem was a double fluorescent tube in her kitchen failed. I replaced it going 50/50 with the cost of the light and the electrician, was I correct?