Focus problem - think it's fan related?

[Phaser]

After a 50 mile motorway trip I was driving back through town and I heard a knocking noise, sounded like it was coming from the front left of the car. Pulled over had a look under the car in case i'd caught something but couldn't see anything so carried on, was fine until I parked up and it did it again.

Coming home it started again and I realised it's when the heaters/fans are on, noise sounds like it's coming to the bottom left of the centre console, down towards where the foot panels are...

Can sometimes get away with them being turned onto 1, but 2/3/4 and the noise definately comes back. No aircon and no problems with overheating etc, the noise can come on as soon as I get in the car or when i've done 60 miles, makes no difference.

Sounds like when you get a bit of paper stuck in a fan, that whirring noise...

Any ideas? Bit of a pain driving round with everything misted up!

 

[Phaser]

Any suggestions to what the problem might be? Haven't a clue where to start looking and I don't wanna take it anywhere without an idea of what's wrong, just asking to be ripped off.

 

[Conscript]

Might be the heater box behind the glovebox....mine makes a clicking noise each time you start the engine or switch the air recirc button off as it closes one of the valves. It's not constant, but its the only ting i can think of checking out.