"...I had read somewhere that mice don`t like the smell of peppermint...."

I read the same thing. Apparently peppermint oil irritates the mouse's (mice's?) respiratory system so they don't want to get near it. Peppermint Altoids ("Curiously Strong") are one of the candies that use real peppermint oil as an ingredient. Since the old mouse-nest-in-the-heater-blower episode in my son's Saab, we've been taking several Altoids and stapling them inside a coffee filter and throwing one of these filters under each front seat. It may be coincidence, but no more mice ever since. We replace each filter about once/year.
--
Current rides: 2005 Volvo S80 2.5T, 2003 Volvo V70 2.4NA, 1973 Volvo 1800ES (fixed the ignition - now back to the brakes again)