As a full time Park Host we have several favorite assigments that have a mouse issue. We have found a string of LED lights around the bottom of the 5er do a very good job of keeping the mice away, not perfect but very close.
I took it a step further and took a section of LED light strip and place around the perimeter of my engine bay, and plug in anytime parked, this has been very effective. Before I did this mice started to destroy the battery jackets in my ram. I placed the lights and replaced the jackets, no issues since.