Rear Suspension Dropped.

[BML]

I don't pay much attention to my 1999 xantia estate and then I noticed that oncoming traffic kept flashing their lights at me. When I started it the next morning the front came up followed by the back and then the back slowly dropped. A local garage fitted a new part but when I went to fetch it they told me that I would need to oporate the lever that lifts the whole suspension right up and then put the lever back to the correct position when the body would drop to the normal running position. If I wanted them to go further and get the car suspension oporating as it should it would cost a lot more.

If I leave the suspension as it is when I start the car up in the morning is it safe to run it?