06 Megane RS 225 a few issues

Good evening all, I've recently become the owner of a 2006 5 door Megane RS in that lovely metallic orange colour and so far I think it's a hoot to drive.

It does however come with a few relatively minor issues but issues I'd like to sort all the same.

Firstly, when the car is warmed up fully (temp gauge very nearly dead centre of gauge) say if I dip the clutch to change down coming to a junction or even if I coast the engine RPM will stay up at around 1200 ish rpm until I come to a complete stop and then the rpm will drop to 800 rpm.

This seems to happen every time. Is that normal for these cars? I can't think it would be.

Second, intermittently the cruise control will display 'cruise control fault' when engaging it and sometimes it will engage and just wait for you to set the speed but pressing the buttons on the wheel either doesn't work or the numbers jump up and down erratically.
The same buttons work fine for the speed limiter so I can't see how they're at fault. It's had a new brake pedal switch fitted recently but I have also read it may be a sticking clutch pedal switch.
This seems logical as sometimes the car will start without touching the pedals and I suppose the switch plunger could be sticking. Are there any other switches which could cause trouble?

Third, both rear electric windows don't work though the fronts work fine. The switch on the driver's door activates the rear child locks and I've also trial fitted a known good used switch which made no difference.
I've heard on the scenic II the R2 connector gets water logged and can cause these issues, is it the same for the Megane hatchback? Does anyone know where it's located? I don't think the regulators are at fault due to only seeing far less than 12 volts at the main power connecters to the rear regulators. I think it was around 4 volts. No clunks or clicks from the rear motors.

And finally the radio reception is dreadful though I've also read it may be corrosion where the antenna base fits which may be causing issues.

I also have another query, if I fit new tyre pressure monitors to the wheels can a dealer or tyre specialist recode them when they're on the car with the wheels fitted? Seems like a daft question but you never know!

It's also got a few more niggles which I intend to put right including worn panoramic roof sliders (replacements now bought), out of alignment steering wheel which I want to resolve as I heard the steering angle sensor may get upset, new brake fluid required as it looks like strong cold tea, a boot lid which you have to slam several times to close, engine vibration from a worn driver's side engine top mount and something else which I can't now remember!

Thanks for looking all, anything at all which might help hugely appreciated.

Chris.