

Then give the car a good shove at the top of the doors so it is rocking on the suspention, you are trying to push the car off the stands.
If you manage to push the car off the stands then they were positioned incorrectly.
If the stands break chuck them in the bin.
Otherwise you can work safely under the vehicle.
This advice applies whether you have spent £1 or £100 on your axle stands. (edited)