floydie: youll probably find the lamp holders are stuffed. as they heat, they transfer the heat from the bad contact into the lamp and it blows. as the bad joint is overheated it often looses its tension, so the problem gets worse.
Blowing lots of lamps in one fitting is a sure sign of a bad lamp holder.
also the bad contact onto the lamps can set up a type of harmonic/noise in the system which may have shortened the life of the TIVO. i once saw an instance of noise on an audio system that only happened at night......traced it to a bad lamp holder in the laundry.
my suggestion is replace the light fittings with QUALITY units. and get your sparky to triple check your neutral (get him to do an earth loop impedance test)
Unfortunately (or maybe fortunately) they are both fairly good quality units, both installed by a sparky. Earth loop impedance test - good idea, will mention it to him.