Car running cold?

I only really noticed this today but after driving the car for about 10/15 minutes, the temp gauge still showed it was running cold (just below the first marking). My car usually runs sat slightly above the first marking and up to the next marking.

I'm not sure if this is just due to the cold weather?

I do sometimes hear a knocking noise when I let off the throttle when it's cold and I did slightly hear this after I had been driving for 10/15 minutes.

Any ideas?
 
I changed my thermostat to a 182 stat earlier this year. Now it's sits bang on the second line at all times and warms up much quicker
 
Basically I removed it from the car and filled the bush full of polyurethane sealant (like tiger seal) it's solid as a rock now!
 
I did mine with urethane but the vibration was ridiculous so I replaced it with a genuine renault one, was around £40