Signs of a bad DMF?

[Mercury00]

I've got a 14 plate Mazda 3 which has been getting gradually worse to drive. Pulling away smoothly is impossible, changing from first to second gear smoothly is impossible and physically quite difficult, upon pulling away the car jerks and bucks, and upon reaching the biting point there is a chattering noise from under the car (I've already changed the engine and transmission mounts, which didn't help with the jerking).

I thought it was possibly the clutch, but it isn't slipping. The car only has 50,000 miles on it, but could it still be the DMF if it hasn't been driven sympathetically?

Thanks.

[GreenV8S]

Could be a damaged / worn spigot bearing, or a broken finger on the clutch. Either could produce severe vibration when the clutch is slipping under load.