Noticed this when going up a hilly section of the dual carriageway at 70mph in 6th gear.

The car is doing just over 2K rpm and I am only lightly resting my foot on the accelerator to keep the speed at 70mph. In doing so the steering wheel starts to vibrate a bit, once I get to the top of the hill however it stops.

What could be causing this?

Meant to say I did a quick search and saw posts about bushes causing the problems/tyres/DMF/brake discs etc.

I've ordered powerflex bushes for the front ARB/Wishbone and also Ibiza cupra Console bushes but won't be fitting them for a couple of weeks yet.

wheels balanced

Could perhaps just be that particular stretch of road?

labouring the engine up a hill ,at that RPM will cause the DMF to vibrate , this is not good for the longevity of that very expensive part

i suggest you drop down to fifth or be on good terms with your credit card company

Yeah i'd go with DMF shudder too. Even though your foot was only lightly on the throttle, the engine was still loaded up because you were maintaining speed while going up hill.

Ok, before getting the car I was reading stories about how not to accelerate as such before 2K rpm, I'll just use 5th for that stretch from now on.

I'll be getting 4 wheel alignment done was I've uprated all the bushes and the suspension.

yup get them wheels balanced