If you have an MSA licence, you can get into the Autosport Show Trade Days on Thursday and Friday for £23.
You need to register here.......https://www.livebuzzreg.co.uk/2017/asi17/
.....and your code is just your MSA licence number.
I'll be there on Thursday. Anyone else ?
As for your original question.....if your proposed motorsport Class requires a HANS device, I would recommend buying only after having tried it out with the helmet and car seat you will use. If the HANS angle is not correct, it can push your helmet forward with coming in contact with the seat headrest.
Having used one for a season now, I would say it is "a good thing", although it is a bit of a pain in the neck (haha...) when you have to reverse or look right round as you will only have about 170-degree angle of view, what with the straps.