air suspension

Hi this is my first post. i have a 2000 plate disco td5 and on my way to work saturday morning my ck passenger side went right down and i started to bunny hop along. pulled car over to self-level car and nothing happene after pressing button. i heard 3 beeps and light was flashing but nothing happened!! parked up and when i got back home i told partner. we went up and hetook wheel of car after eventually jacking it up and we noticed that air bag was flat. managed to get it back home on the back of a recovery wagon!! before we get it to a garage he is going to check out some of your suggestions that people have put on here to see if it is air bag or if it is something really easy. will let ou all know how we get on and if anybody has any other suggestions then we would love to hear them.

Thanks