Strange goings on... Touran 1.9tdi

[Hair Bear]

Hi, this is a Touran, 1.9TDI 105 SE, 2004. 120,000miles.
Car is running absolutely fine, no power losses, no warning lights. DMF needs changing. 1 glowplug failed.
From cold it starts instantly. Hot it always starts but turns over maybe 10 times before starting. It has been doing this for a while.
Noticed last week that the temp gauge was showing slightly cool. Normally the needle is spot on upright but it was a needles width lower than normal. This seemed to co-inside with the fans running flat out. Then noticed that the idle speed was 1050rpm. This was in the really hot weather with the climate control turned right down.
What is happening now is... Start from cold, idles around 950rpm. After about 30 secs revs increase to 1050, fans switch on. Drives as normal. Stop at a junction, rpm 950. After about 30 secs revs increase to 1050, fans switch on. Stop at the side of the road, rpm 950. After about 30 secs revs increase to 1050, fans switch on, and so on etc. This happens hot or cold.
Went to use it yesterday, battery is buttkiss flat! Jump started it, charging ok. Ran exactly the same as before with the fluctuating idle speed. It was put on diagnostic today, result was the duff glowplug which we knew about, the flat battery but no explaination, and something about the fuel gauge sender??? It was just a quick check and nothing was cleared yet tonight it has been used as normal and it's been faultless apart from the hot start issue. No flat battery, temp gauge up to normal, idle speed normal, no fans.
Anyone throw any light on it? Do I need to get it exorcised?
Any help would be appreciated.

[Hair Bear]

OK, spoke too soon!
Idle speed back to wandering up to 1050rpm with the fans again, and now the windows are playing up. From any switch they all will go down using 'one touch', the back will go up ok but you have to hold the switch for both front windows.

[Hair Bear]

And the weirdness continues...
The windows are back to normal - can't explain that.
Still have the temp gauge / engine rev issue, but now I have discovered that if the temp reads below 80 and the revs are up, the heated rear window doesn't work! The light on the switch flashes but nothing else. Temp at 90 and low tickover then both the switch and window work normally.
Beats the hell out of me.

[Crasher]

Are there any codes stored on the ECU? Have you checked the torsion value, injectors balances and injector status digits in measuring blocks? Disable the engine by disconnecting the injector harness from the head and carry out a cranking RPM test, this MUST exceed 280rpm. Clear the injector fault codes after you have reconnected the harness.

[Hair Bear]

Would this be to investigate the hot start issue or the temp/rev problem?
Last time the fault codes were checked the only thing was a 'fan stiff to start' whatever that means. I'm wondering if we're at crossed purposes diagnostic and fault codes perhaps?
Apologies for being a bit unclear but I'm used to working on machines that pre-date the moon landings so a lot of this is black magic to me!

[Crasher]

Would this be to investigate the hot start issue or the temp/rev problem?

All of it. If you don't have a diagnostic system such as VCDS available whilst working on the car then you are really going to struggle to solve the problem, it would turn into a costly time and money guessing game.

[Hair Bear]

Fair enough. I just wondered if the collection of symptoms would point straight to a problem before a trip to the ********.