I've had C-One ARBs fitted to my car today (by ToyotaGT), and they're fantastic !
However, a word of warning. Depending on the age of your car, you may well need to fit new ARB drop links at the same time. The drop links seem to be well-known for rusting up so that they cannot be removed without cutting them off (and therefore destroying them). There's an allen key bolt which commonly ends up just rotating rather than being able to being removed.
Also, on the front drop link, the bottom connector is rather oddly (badly ?) designed, in that to remove it, you have to undo a nut, but then the whole bottom assembly rotates without any non-round piece to be able to get a grip on to stop it rotating.
Fortunately me for me, but unfortunately for him, edeath had already hit this problem and had to abort his installation. But very kindly he warned me, so I was able to go along with a new set of drop links just in case they were required. In the end, a new front set was required. With some difficulty, the existing rear drop links were removed, but since they were likely to be quite worn, I had them replaced anyway.
The list price of four new drop links from Lexus is £198.12 (fronts more expensive than rears)