SLS - Has my compressor packed up ?

I've noticed that my Sll (2001) has adopted a flat or slightly-down-at-the rear stance lately- No SLS warnings on the dash.

recently had a replacement Air spring on the offside. Nearside still ok

So....Smart-person-here decides to raise the rear end via the SLS switch in the dash to see if it will restore the situation.

Result. Flashing SLS Light , now permanently illuminated. Can't hear any noise from under the bonnet and certainly no raising of the rear end.

Does this sound (no pun intended) like a compressor failure ?
If so- are they expensive?
Is an ex-vehicle dismantler option a viable one for this component ?

Thanks
Ian:blabla:

firstly you wont here the compressor under the bonnet because its on the chassis below the front passenger seat. secondly it wont rise if any of the doors are open could be a height sensor but sound like the compressor. proberly burn it out with ur failing airbag.

check the large fuses under the bonnet as mine was doing the same after all the cold weather and its a common fault for the compreesor under the car to freeze and blow the fuse due to water in the air pipes as there is no drain for the system, i changed the fuse and hey presto up she went...good luck oh and the compessors are about 160 quid from the local land ranger garage , buy new as with second hand your just buying the same trouble, you could need the car on the notebook computer to set the heights after the new springs ,

Thanks folks.
The 'Fuse' was an inspired piece of advise.- It HAD gone,
But then after that, the compressor was dead.
New one cost me £280 + labour (Ouch)
Working now though
Ian