Central Heating System Noise

[Kerrangie]

I've recently moved into a rented property. Its an old terrace house that's had a great refurb. My problem is they have fitted a brand new Ideal i-mini boiler. The central heating and hot water works fine but there is an irritating hum around the house when it's on. Its loudest when it comes on in a morning until I turn in the hot tap then it's not as high pitched but it's still there. The pressure is 1.5. Can anyone tell me what this could be, it's driving me mad!

 

[Sharp Point]

Is this more apparent after the heating has been on for a while and the rooms have heated up?

 

[Kerrangie]

Its noisier when the heating comes on first thing in a morning then once the hot tap has been turned on its a bit quieter but the noise is consistent the whole time it's on. If the heating is off and I just put the hot water taps go on, it does it then too