Hi all. I would like to run an 328P at low power, will it be OK running from 3x AA batteries? At what voltage is it likely to stop running?
3 batteries is fine.
If I used the internal 8MHz clock, would that improve consumption much?
The datasheet says that will save you about 4mA.
I want to make a IR remote control, will running at 8Mhz screw the sketch up - timings etc?
That depends on the sketch....and my crystal ball is in for repair.
OTOH you should spend as much time as possible sleeping so running at 8MHz won't save much. If it's going to mess up the timings then don't do it.