Heating pads aren't a good choice for any cage setup because:
1. They can burn the hedgehog
2. They don't heat the entire cage area, so the sudden temperature change when the hedgehog leaves the heating pad can cause them to go into hibernation.
Also, if you have it under a fleece layer under the plastic bin, it definitely won't get hot enough.
I have two 10" CHEs with 100W bulbs and I have them sitting directly on the wire top of the cage and it's just fine. The bulbs are deep enough in the lamp that it doesn't directly touch the cage. You could also hang the lights right above the bin.
Hedgie Mommy to little Piglet
* Abby *