To procrastinate over cool/breathable mattress toppers? Recommendations please!

[whostolemypumpkin]

Help! Our current mattress topper is comfy at bedtime but I regularly wake up in the early hours feeling like I'm lying on a radiator. I've been procrastinating about replacing it for months, but can't decide which "cool" or "breathable" marketing spiel to trust. If you have a topper that keeps you cool at night, please pitch in and recommend it!

Anyone got any recommendations?
Since starting the thread I've dumped our Sareer Gel Foam Topper and replaced it with an Eve topper, but it's no better. I'm thinking of returning it under their 30 night guarantee.

I've heard that wool ones are pretty good?

I haven't bought a mattress topper yet as I would only buy one with natural ingredients that don't make you too hot. I don't think memory foam would suit me.

Why not look on Which or other product review sites?

Why not look on Which or other product review sites?

Most of them aren't independent. Even the Which? reviews now have click-through commission. I probably will look at Which? but will have to pay for a month's subscription as I've already used up my free trial. (But if anyone has an active Which? account and can post a list of the toppers that scored highest for being cool, that would be awesome!)