The Dispatch | Expert | Scudo Hub

Those engines (any) as a matter of fact are designed and tested to operate in in -20°C - +45°C. Thermostat temperature is only the part of temperature management, there's also the shape and positioning of hotter and colder parts of the engine, oil does the other main cooling- circulation- (lubrication)  funcion.
As for the expectation to change coolant temperature to have an effect on diesel "ignition" - hardly, if anything cooling the air intake (making it denser- bigger volume) perhaps could make an impact, but we are talking about 5° degrees change out of 65° operating temperature, never mind other parameters compensating itself to minimise it anyway.
Would lowering coolant temperature make engine more efficient ("work better") - not really
Would increasing coolant temperature make engine work better, more efficient? - not at all, as it wouldn't have no measurable impact on fuel ignition temperature. If anything you would increase a chance for a fluid to boil up at the points where it is getting much hotter, than thermostat housing is.
That applies to all internal combustion engines... at least most off the liquid cooled ones...

Or, as someone on here said  : "aren't broke - don't fix it" or "(keep on) fixing it until broke" 

Mate, I'd love linkies to apps you are using please?
(tried x4 off, either don't connect at all or want money for any functionality)
Thanks!

@Eileen2006 How is it going, any updates?

Couple of pictures would've helped to help you 
Just isolate it, warm up engine couple of times to be sure all is as closed or as open it's meant to be (have normal air intake and don't bother exhaust gas) with pliers, before committing to a proper closure with bolts.

Even replacing the blower motor (w resistor) doesn't necessarily mean it is solved (as happened in my case), down to the resistor going "funny" it typically melts anything it can before fuse would go... wiring, sliders, relays etc, etc

https://dispatchexpertscudo.org.uk/foru … hp?id=1645

https://dispatchexpertscudo.org.uk/foru … php?id=239

if you in to in detail things (not a repair, but modernisation topic (briddy good BTW))
https://dispatchexpertscudo.org.uk/foru … hp?id=1080

https://dispatchexpertscudo.org.uk/foru … hp?id=1780

unbelievable they are still about, but I reckon it's the same firm
https://www.revampavan.com/price-list-2022/

Doubt anyone would be doing custom job worth few times more that of any of our vans worth
Years ago, I was considering investing in a T4 and called around, when some family owned firm (in Southampton) quoted me £4.5k for a standard fibreglass with all stainless manual lift, could have had it in carbon and electrical, but didn't brave to ask for that, as just a normal stripping, templating, supports etc- just labour was about £2k

BUT YOU DIDN'T! 
   

This time it is Waze, down to experience of about 10 years testing every single one there was/is. Data?- it has become a tad more consuming, but in general with data  monitor it's proven to be ~ 100mb an hour of traffic congested driving in SE, I can't be bothered with none other these days, although I got installed 3-5 others on the go.
If anything, I should've bought 15-16mm velcro strips for mouthing all contraption on-off ... but hey-learning curve
Bluetooth?- kinda not needed, as I use 2D maps, glance over (more like looking at it all the time), not the road, even locally... taught me to NEVER argue with "her", no human can possibly be that much aware of all that's happening traffic ways, regardless how knowledgeable you are in the area. Not sure if the "Slab-Tab" can transmit VHF in to radio, thinking along the lines to have it interconnected with nav apps??? dunno, but not necessarily needed after-all, might see what's what at some stage.
ANW, as I (and you) say- don't bother with mounting thingies, natural contours of dash make it all perfect to velcro-it, concur!
Particular Slab-Tab has a SIM slot, so not necessary to tether from the phone, I've set-it up so only new email (and number) accounts are trying to communicate, almost nobody knows the number to call me... so far no disruptions.

Once done driving/navigating, I use it for my in-bed sleep-aid, with all the TV streaming etc, as it was doing my head in, when "watching" telly, falling asleep, getting awaken by something or the other, whilst this one, once folded up in a duvet - can't hear it

briddy good, especially if you understand what are you looking at 
https://www.mediafire.com/file/nejq2h28 … s.pdf/file

not a clue if you have Lucas or Bosch pump, it also most often makes sense to be replacing whole pump, instead of solenoid alone, but those are rather dear...
if it was fixed few extra squids aren't that much on a grander scale of repairs