2002 1.3 Fiesta coolant leak and low speed issue

Hi,

Have 2 questions about my 2002 Fiesta 1.3 if anyone can offer advice.

Hopefully I am posting in the correct section.

Firstly can anyone suggest what would cause coolant to leak slowly on to the top of my gearbox when the weather is cold?

Am I right in thinking the thermostat housing is above this area, as I know they aren't made very well.

Only appears to happen when it's cold at night and only loses about half a cm on the tank.

Not having to top up daily but after a really cold night there is a small puddle under the car and on the gearbox.

Had head gasket done last year so highly doubt it's that, the head gasket was just leaking in the corner and was down to age of the gasket, carpet inside isn't wet and I have had a new coolant expansion tank (it's not that side anyway).

Doesn't happen when driving only when it's stood.

Next query is when I'm driving slowly in traffic etc, the revs don't hold properly and the car jumps a bit, this happened before the leak so I'd say they are unrelated.

It runs normally after a short time of "kangarooing" and drives spot on normally, no power loss or anything.

It's as if the car just doesn't know where to rev to momentarily.

I've had new plugs, leads and coil pack in the past 6 months.

It idles perfectly, starts perfectly and starts to drive with no issues, it just seems to do it when hot or cold while driving slowly without using the clutch.

Could it be a throttle position sensor? 

I've read that someone had the same symptoms with a loose gearbox or worn engine mounts but I expect the result of worn engine mounts would be more drastic.

Hopefully someone can suggest reasons for these couple of issues, thank you in advance.