Might as well replace the cambelt while your at it. A new tensioner will be around £20 and comes as part of the "cambelt change kit". A camblet change on your engine, including a new tensioner would probably cost around £150 to £200 depending. Worth having a go at diagnosing it yourself though first, just to make sure.
1) make sure the engine is cold. 1) Remove the resonator and air box etc from the engine. 3) Remove the keys from the ignition!! 4) Remove the first 2 spark plugs (the ones closest to the cambelt side). 5) Insert the knitting needle into one hole. Make sure it is straight. Make sure it is sitting on the piston. With the belt moved away, detach the belt tensioner assembly and the alternator fixing bolts, before positioning the alternator clear of the timing chain cover. Now remove the six bottom pulley retaining bolts, bottom pulley, main crankshaft pulley bolt and bottom pulley boss. Lower the vehicle back to ground level, remove the ignition coil i use contitech, never had a problem, people have advised me against gates belts. my bravo is on a dayco and has been fine but then again id hope it is after only 2 months , from 'word of mouth'' dayco is seen as the one to go for if not getting fiat parts. and as for cambelt replacements, im going to stick with fiats recommendations on my punto (8 yrs/72k ) still never seen a fiat cambelt go