Hayzzx

Hello, I am new to this forum and wondering if you guys would be able to help me.
I have a 2007 Ford Fiesta and has created an odd revving problem.
I am a bit of a novice when it comes to engines but I know the basics so please don't judge how I am trying to explain this problem!
Basically, when i start my car I understand my revs are highly that usual to warm up the car and normally in a few minutes they lower/settle to a normal idle, well mine doesn't.
It seems like it's sticking (stick between 1000-2000rpm exactly) and sounds awful when I sit at traffic lights as if my foot is accidentally sitting on the accelerator.
My dad has checked any pipes for any air leaks and he can't seem to find any problems. I bought some fuel cleaner to see if maybe any valves we're dirty to try and clear this through, it seemed to have worked for 300 miles (normally revving to idle when warmed up) but this morning it's doing the revving problem again as if it had only temporarily fixed it. The only thing it has done has giving me more MPG.
When it first started acting up, SOMETIMES my car would really struggle to start on cold mornings and when it started up the needle/Rev counter was very erratic for a few secs. Also when I turned my steering wheel in a full lock the car would nearly stall quickly but this has only happened a few times and hasn't done this at all when I used the fuel cleaner.
I have noticed that when the car is warmed up (temp gauge needle is half way which is normal I have been told), that the only way for the revs to be a normal idle is to turn off my car and then quickly turn it back on and then the revs would then lower to a normal idle which is 750- 800 rpm.
This is really bugging me, I have been told it could be numerous things like a dirty throttle body and a faulty/bad idle control valve but I just want a more accurate answer.
Hope this helps! Thanks in advance