DMF=Duel mass flywheel.
If the slave cylinder has gone then you don't need to replace the clutch itself, just the slave cylinder.
Problem is that you need to remove the gearbox to replace it, so if your clutch is quite near to needing replacing then you might as well do that at the same time, as the major cost is the labour of removing the box to do it. If you're handy with a spanner then you can remove the box yourself (i did mine, not too hard, about a days work) and just pay for the slave cylinder.
DMF's wear out and most people change them when replacing the clutch for the same reason, labour costs, but if yours is in good condition and you're skint then you don't have replace it.