Very strange noise,possible release/ thrust bearing bearing?

[Oigoinoi]

Hi all I've just bought a 2003 multispace forte with the 2.0 hdi,a good choice I'm lead to believe within 100 miles of ownership the gearbox( I think ) has developed the most awful rattling/ catching sound it's very loud and is present when the car is under drive in all gears,all speeds worst in 5th at speeds over 50 but not present at all in 4th,the car I did notice had a noisy release bearing but I wasn't too concerned with this,any ideas anyone is it a common problem on these oh it's a manual box.many thanks in advance for help! Also the noise completely goes when coast out of gear and in gear with the clutch depressed
Just an interesting development I've found it made its nasty noise when I increased the revs quickly whilst stationary out of gear clutch out!?