yes Jez, I think a very good noise source (close to white noise) is to use the pn junction noise of a diode(or transistor), I once experimented with it and used rf amplifier, looking on a spectrum analyser I sow a 20 mHz bandwidth noise generator ( due to the BW of the amplifier I guess) and I was impressed with the results.
However as an engineer I'm not going to kill myself generating the perfect random number generator, I just want to get my job done quickly and I think the rand() function would do the job provided I always get a different seeding point at the start of operation of the device, something like once the device is switched on I start a free running timer, once the start executing random targets is pressed, the instantaneous value of the timer would be used as a starting point of the rand() function as has been suggested by experts on this forum in previous threads.
regards
Mahmood