I have a Brompton and I like it a lot, it was a superlight too.

But honestly, all factory installed components are low quality and heavy !

To have a lightweight Brompton, all components must be replaced and this is also what happened on my Brompton, only the frame is factory and even a part of it, the rear titanium triangle, was modified to 135mm OLD.

So building up a full bike from a titanium frame is also a good option and cheaper than starting with a 2s superlight.