thats just going to mask a problem...if it works.

try doing a couple of tests.

1. with the handbrake on see if you can fully release the clutch in first gear, engine running.
2 if say doin 50mph in 4th and you boot it do the revs shoot up and speed do bugger all?? (more noticeable on a hill)

even without doing those checks i would say you're clutch is nackered and if it doesnt do any of the above its prob very worn and needs changing!!!

ps, i'm an experianced(ish) focus owner. my mum had a w reg 1.8 petrol for years that i learnt to drive on and drove for first 2 years i was on the road. that needed a new clutch after my bro landed his glider out in a farmers PLOWED field and we had to to the trailer accross the furrows to get to him...that didnt do much good for the underside either tbh.

and i have had my w reg 2l petrol for just over a year now. clutch gott replaced before i got it though at about 74k.

hope this helps