Whining/humming Noise When Cold Mk7 Fiesta

Hi all I have a 2009 fiesta 1.4tdci. Have owned it for about 2 months now and so far so good apart from having to go back to get injector seals done. Its got 32k and its started to make like a whining or humming noise which is worse when starting from cold. Its not that part behind the stereo as it sounds like its coming from the left hand side of the engine when your sitting in the car. Also it fluctuates with the engine speed. Once warmed up it does almost vanish but you can still very faintly hear it.

I did mention it to the mechanic when I took it back to get injector seals done and he said he couldn't hear much but the car had warmed up by then. As its still in the 3 month warranty I will take it back again but would like a bit of info as to what it is first. Im a fairly good diy mechanic and know it shouldn't be making a noise like that.

I did read something about a pump that activates when its cold to keep the emissions down???? Was just something I read on a forum and was a bit vauge.

Any help much appreciated.

Thanks

Paul