I had this problem too when being pushed in a wheelchair. Horrible. It was very speed dependent for me and the person pushing just HAD to go a lot slower. For me it was about 1/2 their normal walking speed which made things pretty frustrating all round But any faster and it was just terrible. It was very much a vertigo sensation for me.
This combined with the fact that I don’t have the strength to self propel any more is what prompted me to ditch the manual wheel chair all together in favour of my micro scooter. I can whizz around 3 times as fast as someone can walk with NO vertigo at all
For steeper and rougher outdoor scootering I have my big scooter and my micro one lives in the boot of my car. No more vertigo and no more need for someone else to push me around. YAY independence
I got funding for mine. I have no idea what funding arrangements there are in the UK but I am sure someone could help with that if you are interested in going the scooter route.