There is definitely sour cream at the Migros (Sauer rahm), which is pretty close to the American version (it is not as thick, though). It's with the cream, double cream, etc. I'd stay away from the Sauer Halbrahm. As for cheddar, the stuff at the Migros is a pretty poor substitute (but, then again, most "cheddar" in the US is pretty nasty as well), but I'd bet Globus has something more palatable, and they'd probably let you taste it!