Well does breeze block show outside or is it sand cement rendered? I cant see how you cant know but anyways

Yes all paths and soil etc must be below the height of the garage base or water WILL get in.

Heating a garage with no insulation is complete bollocks and a waste of time and money...you will still get damp.

you need to make sure all ground level like i say is below the concrete base
Make sure there is plenty of ventilation....even if it makes it a little bit colder, cold doesnt rot a car and cold doesnt make condesntion.
Run a little dehumidifier just to take away some of the moiture in the air.

My garage is well ventilated and i run a small dehumidifier and everything is bone dry