1. brakes are a little soft at speed, though they grab at very low speed (I will ask the workshop to check the pads - not sure if that was done last service)
Probably brake pads and or discs - wear and tear item, so not covered under warranty
2. on occasion, I have noticed that when I turn the steering wheel fully to stop to the right it is followed a half second later by a single faint knock felt in the steering column
Could be a track rod end or a bottom ball joint thats gone, may be covered under warranty.
3. when decelerating to a stop, just before actually stopping, the revs dip to ~500rpm and the engine judders, before adjusting the revs up to the normal 800-900rpm. Similarly, when starting up, there is a second or two when the revs hesitate at ~500rpm before adjusting up to normal, with the same juddering
Sound like a sensor needs replacing to me, either IAT (idle valve) sensor or temp sensor IIRC.
4. two or three times a week, when at low speed and the engine is under extra load, eg when I accelerate up a steep incline, and the gearbox is changing up or down through 1st and 2nd, the gear change is extremely rough, a very hard thud
This to me is the most worrying, as the autoboxes are not reknowned for being the most reliable and are expensive to get fixed. Get this checked under the warranty while you can.
Of course Im not expert, so could be wrong on all counts !