does the car have factory fit hid lights? that's the only legal mot reason needed for self levelling, otherwise it's just a comfort thing, if your happy to sacrifice comfort (minimal difference) then i'd go for the cheaper ones, but if you have factory hid's then it's all down to the mot tester, if he wants to be strict he can fail hids of the correct requirements aren't met, they are
self levelling suspension
projector unit for the hid bulb
headlight washers