Just got back from a week's holiday in Tignes in the French Alps. My '08 TDV8 did the 1400km round trip without problems but on the way down through Switzerland I started to feel a vibration through brake pedal and a shuddering of the steering wheel when braking from around 100-120kmh (60-75mph). Braking performance did not seem to be affected. Braking from slower speeds did not cause the vibration and neither does it occur when cruising or accelerating.

I also noticed the phenomenon on the return journey. The car is due to have its summer tyres put on next week so I told the dealer about the problem and he said we can try to replicate the problem on the local autobahn at the time. However on my local drive to work and back, which is only 40km each way, I've since realised that the problem does not occur. Could this be due to the brakes not being hot enough due to the short distance?

There had always been a slight vibration or 'pumping' sensation detectable through the brake pedal but I always assumed this was the normal affect of the ABS system actuating the brakes and it had never caused the steering wheel to shudder back and forth.

The car passed its MOT without problems only 6 weeks ago. I've had the car for 2 years and the dealer had put new discs and pads on the front and new pads on the rear wheels and I am still using them. I've done 32000km (20000 miles) in those two years. Anyone experience the behaviour or know what the problem might be? 2012 Vogue 4.4 TDV8 automatic (LHD), Santorini Black
2008 Vogue 3.6 TDV8 automatic (LHD), Java Black

Sounds very much like warped discs, especially as it only seems to happen under braking. I would get the brake discs checked over to be sure.

^+1  2006 (56 Reg) 4.4 V8 Vogue In Bonatti Grey (Gorgeous!!)

Yes, checking discs for oscillitation is a good way to go,
other causes to investigate: tyre pressure? cupping of the tyre profile? the road surface where it occurs?