Engine Vibration At 25mph / 1500rpm / 3rd Gebasically As Per The Title

[ABT]

Basically as per the title. Citoren C3 1.6 hdi Exclusive 2007. When in third gear doing roughly 25mph at around 1500rpm, there is a vibration which seems to be from under the bonnet. It almost sounds like the exhaust blowing, but the exhaust's fine. The noise seemed to start after the car went in for an oil and filter change, and fuel and pollen filter. Any ideas as to what it could be would be greatly appreciated. Makes no difference to driving the car, but it's driving me mad. As I don't know anything about cars, any 'strange' noise worries me!

[ABT]

Following on from my earlier post. Think the vibration noise is coming from where the cover which goes over the injectors and the air filter housing meet. (Had to be told that it was the air filter housing!). The air filter housing moves slightly, and when the cover is removed from over the injectors, there is slight powder on the underside of the cover where the air filter housing sits below the injector cover. Does anyone have any ideas as to why the air filter housing appears to have a bit of movement? Also, the air intake hose next to it has slight movement (more than it probably should). The 'bayonet' fittings on the air intake hose keep coming apart, so it's now held together with gaffer tape! Any thoughts?

[biggestalever]

I had a really annoying buzz and vibration at certain speeds. Checked all the air intake stuff, even changed exhaust cos I had convinced myself it was the flexi joint..

Turned out to be, where someone had hit the front valance whist parking head on, the bottom radiator mounts had popped out of their retainers. Pushed it all back together and bent the little blighters back into shape and all ok again...