Is the car showing any fault codes/engine management lights?
How many miles?
When revving the car up stationary in neutral does it still judder?
Ok..Going by what you have said and the engine appears to be running ok and doesnt appear to be missfiring..normally that would happen too at idle and not just under load....the fact you dont have any eml light on nor any codes stored that is known off even in pending or history.then its sounding like the engine is ok...then id say likely source could be likely the clutch itself maybe at fault..or problem on surface of the flywheel..thats causing the clutch to judder..that could be something for a garage to maybe investigate on or certainly to rule out.aswell as checking obviously transmission.engine mounts for excess wear..that maybe transferring vibrations through the car under load..
Could well the same thing..ideally you want be rulling out those areas above..but if its still under warranty which you do have 30days from purchase to allow the garage to fix the problem or ask for a refund..