To add to this I personally think Ifor Williams is loosing it's way the last few years new trailers the partition has to be tied to hold closed due to to thin metal used. The plastic hinges that hold the vent break very easily just in normal operation, and this by the person who paid for the trailer not just an employee, the older (15 year) box is more robust although the brakes have never been up to the modern trailer.
Now to be fair that was last year and the newer versions have resolved these problems, something I won't be looking at for a few years, but this does mean these lower quality trailers will be on the market wanting to be sold.
I've you are in a market for a trailer take a look at Hudson, they seem a lot more solid, like the Ifor's of 10-20 years ago.
They also have a drop down front for when running with an empty load and reducing the drag.