OK i know they may not be suited for a mechanic working on oily floors but i got these from Toolstation and they are the best boots i have ever had.
http://www.toolstation.com/shop/Work.../sd3246/p25859

I have been through load of boots like Dewalt, CAT, Timberland, Scruffs, Vital etc and these are the best by far. Feel like slippers

cheeRS

Chris