To be fair, the £50 includes a charge pump. If you don't know already - a charge pump requires a constant pulse-train from the controller (PC) before it enables the spindle relay... to avoid inadvertent signals from the PC inadvertently switching the spindle on... ta da!, that's the real solution to your problem.

Anyway, ignoring the charge-pump functionality, the boards are functionally similar, though as you might expect the £50 card a bit more refined, although that one in particular looks very similar from a component count to the Chinese board. Both offer a 0-10V PWM driven output.