I'll agree with shona that both pronunciations of garage are used over here. There is some degree of class differentiation (-ahj being "posher") but that is fading in these more egalitarian times, thank goodness.

The major difference between the Brit version of Gar-ahj and the Merkan one is in where the stress lies. Britons put stress on the first syllabe, regardless of which pronunciation is adopted, whereas (so far as I know!) Americans put the stress on the second syllable.

As to "on-vel-ope" or "en-vel-up", I also admit to using either, probably fairly equally.