More than likely water ingress with the weather we've been having

Is the interior steamed up and lots of condensation?

You can try this eBay link and think you'll find most of the parts you need

https://www.ebay.co.uk/b/Vehicle-Parts-Accessories/131090/bn_1838652?mkcid=1&mkrid=710-53481-19255-0&siteid=3&campid=5338906902&customid=&toolid=20012&mkevt=1

eBay is sometimes best place to value the car by setting a high reserve price and seeing how the high the bids get to, you can always withdraw it from sale if the bids aren't high enough

I'm sure a garage could find the issue as it could show as excess play in a component due to wear and tear possibly?

Thats a fantastic looking GTC you have there, great paint colour as well

Good to have you onboard!

I guess ebay is probably the best place to source most parts for the Vectra

https://www.ebay.co.uk/sch/i.html?_from=R40&_trksid=p2334524.m570.l1313&_nkw=vectra+door+seals&_sacat=131090&LH_TitleDesc=0&_odkw=vectra+exterior+trim+parts&_osacat=131090

More than likely the turbo variable vanes have gummed up with carbon, especially if the car hasn't had a good blast for ages this tends to happen

What temperature is displayed on the instrument panel?

generally, the thermo-syphon effect within the cooling system means that the top will be hot and bottom will be cold and the coolant circulates (with the assistance of a water pump) within the engine and ancillary items such as the heater.
Therefore the bottom hose should be a lot cooler than the top one.
If you measure with an infrared temperature gun, the temperature should fluctuate (without any sharp dips or peaks) throughout the engine.
 

Its a turbo coolant pipe

There are a few listed on ebay

https://www.ebay.co.uk/sch/i.html?_from=R40&_trksid=p2499334.m570.l1313&_nkw=meriva+turbo+coolant+pipe&_sacat=131090

Here is an eBay link to some Meriva steel rims

https://www.ebay.co.uk/sch/i.html?_from=R40&_trksid=p2499334.m570.l1313&_nkw=meriva+steel+rim&_sacat=131090

Not sure of the exact part number you require but I can recommend FAI as a first class gasket manufacturer as have used them extensively as a preferred company in the past.

Elastomer is the compound that is pretty much a silicon bead used to seal the various components on the head and block. 

Apart from resting your foot against the clutch pedal then possibly it is sensing some slippage through the clutch (in fact loss of wheel traction) which may be interpreted as clutch slip?

It could still be the battery supply which could dip and then the battery recovers by the time you have measured the voltage (e.g. warmer air temperature) so I would run a deep discharge test (measure the volts with the engine off and the lights on - should be around 10.8v to 11.5v minimum).

Otherwise, could be water ingress in the electrics so if there are any leaks internally I would start there

Hi Mr Boyo ..... welcome to the Club

 

Very nice but such a shame to see it resting in the field

I had one years ago but it definitely did not look like that one

Thanks for posting the photo

Have you got an engine code handy as this would define which engine is fitted

Hi Andy

I believe it is just an interference fit

Do you have the new cable to hand as it should be tapered or have some clips which go in but won't come out without compressing them

Hi kidsmum04 ....welcome to the Club

Fine looking Insignia and I see you have had some snow as well

Good to have you onboard!

Hi PauloVXR ....welcome to the Club

Good to have you onboard!

Stud extractors if they are seized otherwise flexi-head spanners if they are inaccessible 

Hi M-C Kazza ....welcome to the forums

Good to have you onboard!

Hi Hangonrose ....welcome to the Forum

Sounds like you've got a great car there, worth keeping on top of the maintenance and I'm sure it will keep going for years.

Plenty of information in the Meriva section in these forums to give you an idea of common faults, etc

Good to have you onboard!

Hi Tricky .... welcome to the Forum

Keep us updated on the mods you are doing, would be interested to see how it turns out 

Good to have you onboard

Have you first tested the battery condition and charge? as this can cause the EPS fault if the voltage drops low, which can occur with this cold weather

Advisable to check this first and then replace the battery if necessary

Have you checked the side repeaters on the front wings or mirrors?