Great idea. I have had one for years and they really reduce the effort, hassle and physical work needed. If you put them in a race and include a footbath and a shedder at the end of the line, you can get a lot of different jobs done in one go.
I have a Batemans which is virtually the same as the WM Iron works one. I believe at one time there was some arguement over patents infringement or something. Their joint design is different from any of the others in that it: Allows an animal to run right through the machine should you just want to use the race for something else. It turns right over either in line or partially out of line. It allows you to take the animal half out of line to dag more easily and has an automatic head restrainer as the animal tries to push through. It is adjustable for size but that bit is fiddly so, as your previous respondent said, it is not really much use for anything under eight months old. (however if you have a lot to do you could set the size and then run a batch through OK.
At the Royal Welsh a couple of years ago, I suggested to Bateman's that they incorporate a tray for markers, drenches etc. I also suggested a few other minor improvements but, as they did not bother to reply to me, I don't know if they have changed anything.
There is no doubt that if you are handling 200 or more. A crate such as the one 'barnes' recommends is a good buy. I believe they now cost about £800 but when I bought mine it was £250 and, although expensive at the time, has made the job much much easier. There are cheaper ones on the market but in my view they do not have a many useful functional features.
As with any race however, one of the key things is to get the sheep in and encourage them to keep moving. I use a race with covered sides and a covered pen area. In this way the only way they can see to the fields is down the race and the backside of the animal in front.
All the best and let us know what your decision is.