I've also bought an ultegra di2 from AliX which works absolutely fine. All parts pair up with the Shimano app which implied to me that they are genuine.

In terms of warranty, I would have thought that Shimano would deal with that themselves? What woul dhappen if you bought a groupset from say, Wiggle, in the UK. Who have now gone bust. You'd be in the same situation?

Fingers crossed I don't need to test this assumption

I've been chatting briefly with RK Ultra Extreme Carbon Fiber Store Store on AliX based on trawling through this thread.

Almost ready to pull the trigger, but just have a question about the difference between 'ordinary' and 'ultralight'
all i can get from RK is that the difference is 'Lighter weight and better materials', but can anyone else provide a little more advice, what did you go for and is it worth almost double the price?

Ordinary ￡651.19
Ultralight ￡1,146.19

https://www.aliexpress.com/item/1005008069790512.html?pdp_npi=3%40dis%21CNY%21%21CN%EF%BF%A5%205%2C000.00%21%21%21%21%21%402140c1e917485128794208717e4fea%21%21im%21%21

Thanks!