2012 1.4-litre TDCi Zetec 1st gear issues

2012 Fiesta 1.4-litre TDCi Zetec
30,000 miles.

Issue I'm having but it is only very occasionally that it ever happens.
I mainly got this on a certain stretch of dual carriage way that is 70mph but has unbusy roundabouts about ever 1km which you could normally go straight through in 3rd or almost stop and proceed in 2nd.
The engine fan will come on and be whirring loudly. It doesn't stall but it does feel like it will. The main issue seems to be that as soon as the clutch begins to release the revs shoot right up then drop dramatically (the engine noise changes and it feels like its loosing all power but as soon you release further and accelerate its ok.
On a steep incline its actually impossible to not stall it as straight away that you begin to raise the clutch it would stall no matter how quick you are on the accelerator. (basically it will stall before you can even reach a biting point).
Turn off the engine and the fan will continue for about 30 seconds. Normally then restarting it would be fine but some times it would continue until engine has been off for a couple of mins.
Even when stationery and in neutral the rev counter will be moving up and down quite a lot.
Driving in the correct gear for the speed and I get that shuddering feeling as if I'm in a gear to high for the speed I'm doing. But you drop down and the revs are way over what they should be.

Any info would be appreciated, even if its to tell me its something I'm doing wrong that's probably causing it!