Just to update this post. Ive been keeping an eye on the level and made sure
that water is circling the engine properly (valve on the right hand side of the
radiator and at the back of the engine bay) the light went off a few days ago
and hasnt been on since. Ive done several hundred miles and its fine.
No changes have been made. Probably a faulty earth I recently had the power
steering pump seal fail and covered the engine in oil. I still dont know where
the Water Level Sensor is, no mention in the Haynes book. Although theyve
changed it now to a "Service and Repair book" not as thorough as it used to be.
The Temperature Sensor is mentioned, and this is on the block, I assume its part