Where is the best place to mount the Air Temp Sensor i have with my MS2 loom please?

In the air box, or if your running a pipercross or similar in the back plate.

No filter? Just fasten it close to the inlet trumpets.

If you look at any production setup you will see they measure the IAT close to where the air enters the cylinder head either in a branch of the manifold or in the plenum close to where it joins a branch.
The IAT is usually a lot higher than than ambient air temperature.