Assuming your car doesn't have height adjustment, would it be worth doing the job properly (and safely) by finding a replacement seat from a breaker?

You need to be very careful using cushions on car seats, they can compromise the way the seat/person reacts in an accident resulting in serious injuries when without a cushion injuries would have been small or possibly even zero. Claiming for personal injuries in such circumstances will be difficult.

Manufacturers have huge resources that research comfort and safety and any changes will almost certainly have an effect.

Perhaps you should have researched more carefully before you bought the car and found a comfortable on in the first instance.

Thanks, yes, that is the real answer. I need to slow down a bit.

You could ask a workshop to fit some spacers/washers between the seat fixings and floor, but it will need more modification if the seat needs to go higher.

The problem with cushions is that they stop your body making good contact with the seat, reducing support. I find that lumbar support cushions are way too thick for example.