The LED modules, heatsinks and voltage arrived, so I quickly put them together to see how well they worked/looked. After hearing some horror stories about dodgy eBay LEDs, I was pleased to see that all 100 diodes in the module lit up correctly.
The modules are supposed to run at 35-36V, but I gently ramped up the voltage as I didn't know how good the heatsink was. Here's the LED running at 25.6V.
Here's the LED running at 27.9V. The workshop lights were still on in this photo, but the LED drowns them out :-D.
I left it running for a few minutes, and the heatsink was barely warm. I'll see how it goes at higher voltage, but if it gets too hot, I do have a couple of CPU heatsinks with fans. During the run, the leads from the power-supply got a bit toasty though. Oops. I should really get some better ones.