mate it will be the clutch i have had about 20 or so x reg polo's in with the same problem port of call for these are the clutch's go , clutch cable and also the pedal box splits the only way round it is to do all three really it does become e little expensive but it really is the only way of sorting it out first thing to do is have a good look at the pedal box as it plits if it has do that first and fit a new clutch cable remember that when you adjust the clutch cable you have to have a set clearance between the coils on the spring. if this dont work the do the clutch but be warned the pedal box is a night mare to change

list of parts

new pedal box
steering colum sheer bolts
clutch cable
clutch
gear box oil

and a lot of time and patience