Hi Leon,
I experimented with peltier cooling some time ago, all I did was get a couple of peltier devices from Jaycar and stack them onto a fan cooled heatsink from an old PC.
The cold face got down to -25C with a little aluminium heatsink attached to simulate a thermal load from, say, a big ccd
Frosting/dew will be an issue.
I notice you have frost all over the cold face but the thermometer is reading +16C? Should be less than 0C to get frost... I see the thermometer's sensor is bolted to the cold face, but perhaps the actual thermal sensor is in the body rather than the mounting ring... and it's not in contact with the cold face. See if you can get the sensor body right up against the cold face
Cheers...
Rob