I've found the problem (and the ECU). Whilst I was under the car doing an oil change I had a look around and found the Directional Headlamps ECU. It appears that when the clutch was replaced they had indeed disconnected the ECU cable and then failed to reconnect it again. I plugged it back in and the whizzy lights are back. This is good news and means that I can keep the car :) . So, the directional headlamps ECU is in the engine bay, on the near-side, towards the front (near the clutch) and is best accessed from underneath (the connector is on the underside).