Thanks for the replies. I do use the electric hens but I'm moving to larger batches (50 hatched at a time) so even the largest is only good for about 2-3 weeks at best. My current brooders are pallet boxes so about 1m x 1.2m so again, not big enough past 3 weeks, or maybe before. Idea is to move them at that age to larger indoor pens with a lamp. I generally hatch at this time of year so it's getting warmer but can still have cold nights.
The dull emitters look good. Are they considerably safer than the standard red lamps? We used to raise pheasants when I was a kid and lost loads to exploding or failed lamps. Also don't want to burn down my barn if I can avoid it!