These aren't especially easy to find in the UK, and they seem quite expensive for what are basically two folded pieces of fairly cheap metal with some holes drilled through them. The prices at Thomann don't seem much different from anywhere else, and they do seem to have better availability than I've seen on UK suppliers.
Other than the complaint about the price, they do the job very well and have allowed me to mount my Zed-18 into a studio rack. They come with all the screws you need and some instructions for mounting. They were very nicely packaged and everything arrived completely intact with not a single blemish. They fit perfectly and they screw onto the mixer without any trouble at all, very easy to install.
I'm happy I've been able to rack mount my mixer. Really, really happy. I wanted to deduct one star overall because of the price, but I don't think that's a Thomann issue.