Hi chrisbhewson,
I noticed that you registered with your email as a username which may lead to spambot harvesting your email and adding you to their lists. If you like I can manually change it to just the part before the “@” or to any other username you like.
You can read about the different factors that can combine together to affect sleeping temperature in post #2 here including the mattress protector or sheets you may be using.
Wool is among the most effective temperature regulating materials so it may be well worth considering a wool protector, mattress pad, or if you like the “feel” of thicker layers of wool then even a thicker wool topper.
Of course this is about the layers that are under you. Cotton and Bamboo are both very breathable (I would probably give the edge to bamboo but it will depend on the specifics of the fabric). Fill power and the amount of down and feathers in a comforter will also make a difference along with the temperature in your bedroom so it may be a matter of adjusting the temperature or using a lower fill power or less material (different season) in the comforter. There are some guidelines here and more here for down comforters that may be helpful to get a sense of what may work for you and some guidelines here for down alternative comforters as well.
It may also be worthwhile considering a temperature regulating comforter like this or like this that uses outlast in the fabric which is a phase change material that can also help regulate temperature.
Phoenix