Hmmm...interesting. Removed cap, turned key on, temp high, wheel to 3 dots red and checked. Sorry, fan was on. Coolent was low but no warning on dash. Could not see the drip from inside the expansion tank just below the cap but could hear a whining sound (perhaps the aux pump?). Filled the coolent up to correct height for the measuring float. Still no drip (but perhaps I didn’t wait long enough). Started engine and looked down into the tank and I saw drips from just below the cap inside.

Thanks for the images. Trying to find out if my iCarsoft one will do the job. I have also heard of another port under the bonnet of my car so maybe I need to connect there with an adapter.