Just found this full WMB review on another forum. Seems a fairly unbiased review (for once).
B’Twin 100mm dropper £55
4,5 out of 5
This dropper post from Decathlon only comes in 31.6mm diameter, drop is only 100mm and the last 20mm takes a good thump to get. However it’s £50 cheaper than any other dropper we’ve tested and more functionally sound than most several times it’s price. At 665g it’s not a bad weight and the side bolted lay back saddle clamp is secure and easy to use. The under the saddle ‘rodeo grab’ release lever means no cable rub or routing to worry about and I’ve it’s suprisingly easy to use on the trail. The action has stayed smooth, consistent and wobble free, making it a total bargain.
So my few brain cells have worked out its about 100g heavier than a reverb but your wallet will remain £150 fatter. Usually if you buy cheap you buy twice, but £30 is probably worth a chance.