I have one its great. My horse stopped head shaking (which was only seasonal). I got the western one as that is the one I tried her in and it was £80 for leather. I havent done much schooling in it, only hacking, although did have a jumping lesson in the first couple of weeks of having it
We tried one on our pony but my daughter diddn't think he went very well in it , he was quite naughty and ran off with her! so she gave up on it. you can try them out for a couple of weeks and send it back for a full refund if you dont like it, dont forget you can't use them for compertitions,rc or pc , but have a go and good luck
Some people/horses love them some hate them. I think you really need to try one to find out. They offer a 30-day moneyback so if you don't get on with it, you lose nothing. I drive my mare inone, and it has solved all the problems she had.
I can also point you in the direction of a saddler who makes biothane ones for just £30 + P&P