Just wondering how these stack up to the OEM ones, or are they better and whether it is reasonably priced?

NB8B; Big Brakes > GBP 37.39 (after 25%) + GBP 33.71 (postage) = GBP 71.1 (circa AUD130)
http://www.mx5parts.co.uk/information/latest-special-offers-email/