I've just got a version of PlayTZX work in in MacOS X.  It's a programme that takes TZX files and plays them as audio so they can be loaded on a real ZX Spectrum.

I found some old source code on World of Spectrum, last updated in 2003, and which wouldn't work on a modern OSX.  I've fixed it, and managed to get it to load 'Match Day' on my Spectrum.

It's a command line application, which isn't much fun, so I'll add a GUI and make it available to anyone who wants it.