The 10 watt LED arrived. It wants 9-10 volts and a maximum of 1000 milliamps. So I soldered up a driver.
The driver consists of: a 16v Lipo battery, feeding a step-down board that lets me adjust the voltage, going via an ammeter to the LED.
At 8 volts, the LED is just about glowing. At 9.6 volts, it's so bright I can't look at it, and it's pulling 500 milliamps, so that's about 5 watts. I could turn the wick up some more, but I put a thermometer on it, and it was getting hot.
So, I'll need to mount it on a heat sink (a lump of aluminium, or maybe copper; I can use something from an old CPU fan. I also need something to make it blink (I have something on order that might work).
I've also got a 3w red LED on its way to me. Now that I've shown that I can drive the white LED, I'm pretty confident that I can drive the red one.
Also - I've ordered daughter.1's birthday present. It'll be a surprise!