Ideally you would fix the air bag leak (replace with second hand unit). You can actually pump up the whole system manually. It's a bit fiddely though it can be done. Instructions are at www.roverrenovations.com. The system will only stay at the one height, and the computer will not operate anything.
Either which way you go, you would need to fix up the problem before you get the fault code cleared.
The software is called EASunlock
The Hardware is called the EAS Buddy Box