Ewan, the best way to use leelling ramps is to leave the van hitched to the car. Place the ramp in front of the wheel on the low side, then drive up the ramp until the van is level across the width.
Then chock the wheels and apply the brake. Un-hitch as normal and level front to back with the jockey wheel. Then lower the steadies.
If you have a twin axle like me, just back onto the pitch about 4 feet further than you want to stop at. Place two ramps at the low side as before but spaced in-line and apart by the distance between the two wheel centers, in my case about 36 inches.
Just drive forward up and over the first ramp with the front wheel of the van and then drive the two wheels up their respective ramps to obtain your level across the axle.
Chock and brake as before and level front to back as previously described.
Pulling off is just a case of hooking up and driving forward away from the pitch and walking back to collect the ramps.
Simplicity my friend, it just takes a bit of planning.
I do it like this as I have little to no pulling power in my arms/shoulders due to arthritic problems and also having a 1365Kg caravan.
Steve.