Engine slow to warm up?

[9000TURB0]

Hi All, I have a 1996 9000 CSE Auto, only had it for about a week, it used to be my dad's.
I noticed that the temp gauge occasionally takes longer than usual to reach half-way, I have a 15-20 minute drive to work each day, and on 2 occasions it has not reached half-way by the time I get there.

The gauge also seems to go go down noticably before reaching half-way whilst driving, although the fan seems to be kicking in when I stop.

I've had a search on here, but most of the posts seem to be about overheating/ gauge going up too far...

Anyone had a similar problem or can offer any advice please?

If I do get a new thermo/ temp sender can anyone recommend the correct bits to get or a good place to get parts (UK, West Yorkshire)?
Also, if I should be getting a certain kind of coolant too?

Am going to be servicing myself, so will be using this site alot I expect.

I had a 2000 9-3 lpt before this, and am loving the feel of the 9000 - such a nice, comfortable ride!

Thanks
Paul

[Superaero]

New thermostat first. Coolant is standard green glycol.

The later 9000 have weird temperature gauge and fan control software. Replace the thermostat first and then see.