I decided to leave it for a few more drives to see generally what happens.
I made some notes from my drive on tuesday, my temp gauge looks something like this one whereby it just says normal.
Outside temp about 22 degrees C
Motorway driving into the wind about 80 km/h the temp needle was on R
Single lane road with the wind behind me between 70 and 80 km/h the needle was on M
Driving at about 20 - 30 km/h the needle was on A.
Pre grill temp was almost always on N
My feeling is that the grill block is deforming whilst at speed and I was driving into the wind, and thusly allowed alot more air in, hence the lower temperature.
I normally dont do any city driving, but due to the sensitivity of the Zetec engine I would prefer to keep it on the cooler side, right now my aim is to keep the engine around R and no higher than M.
First I will remake the upper grill block, then the next step will be to make a new lower grill block, I'm thinking two slots running almost the entire width of the block, and see what the outcome of that is.