On the AA website there is a section about the new MoT regs and it is reproduced/copied below:
Products on the lens or light source that obviously reduce the light's intensity or change its colour will become a reason for failure â€“ applies to front/rear position lamps, registration plate lamps, stop lamps, rear fog and direction indicators,
Headlight requirements are updated to take account of the particular characteristics of High Intensity Discharge (HID (High Intensity Discharge)) lamps.
HID headlights can cause dazzle if they are dirty or aimed too high, so they are generally (if light output exceeds 2000 lumens) fitted in conjunction with headlamp cleaning and levelling systems. Where HID or LED (Light Emitting Diode) dipped beam headlamps are fitted the tester will switch on the headlamps and check the operation of any headlamp levelling and cleaning devices fitted.
The car will fail if a headlamp levelling or cleaning device is inoperative or otherwise obviously defective.
So it seems that as my car has ordinary headlamps the powerwash system does not fall within the new regulations.