The linkage comes off easily on the BX and CX, the GSA is a different arrangement. Here's the BX rear corrector linkage:
On the left is the familiar clamp to the anti roll bar and at the other end is a brass bushing that fits into the sub frame. This bushing wears over the years and gives excess play. Worse, the rod of the linkage wears in the bush giving more free pay. Add to that a sludgy height corrector it'll cause suspension that's too high some times and too low at others (also makes the intermediate height position a bit vague) Also in the picture is the modified brass bushing I had made with closer dimensions to fit the sub frame and to use a different part of the linkage rod to bear onto. There's also a spare original type bush pictured.
Here's the worn bush - can just make out the worn area (shiniest bit)
Here, the rod end part and the bush.
If you look at the rod there's a wee blue paint mark on the end and about 1/2" in from that you can see the corresponding wear on the steel rod. My new bushing attempts to get the rod to pivot on a different unworn area nearer the blue paint.
Here's the new bush fitted in the subframe, on this and the old one there's a steel clip secures it in the bush's groove - I made the groove slightly closer to the subframe so it was tighter but it wasn't needed as the new bush was a stiff press fit in the sub frame.
And here with the linkage back in place and plenty of grease in the bush and the fork that fits onto the ball joint on the corrector unit.
Height corrector had been full of black LHM
The ball joint of the corrector can wear too as can the fork end of the linkage lever on the rod above. These can be fixed too. The ball of the corrector can be carefully turned in its fixing using some good grips and a vice. It only needs a slight turn to move the worn flats away. The fork end has corresponding wear, the excess gap can be reduced after doing the previous ball join fix by taking the newly fixed ball joint and fitting it in the fork while on the bench - then getting your mole grips or vice to squeeze the fork around the ball - it'll bend that tiny amount needed while leaving the tiny clearance necessary not to jam up.
Here's the ball and fork just apart for the CX front corrector and linkage
All back together, reset the normal ride height and welcome to factory spec suspension again!
) but on mine, I found that I could get a spanner into the furthest forward pipe at a long reach and unwind it in careful and annoyingly small turns. The third pipe that's beside this one, it is the return and it joins straight onto the rubber return pipe junction 'octopus'. I found that you can't undo this pipe using the spanner but you can LOOSEN it. If you loosen it then remove the 2 mounting bolts, remove the corrector linkage (one 11mm bolt and pull along anti roll bar then turn 90? and route it out) and then remove the other two easier pipes it leaves the corrector disconnected from everything except this last return pipe that is now loosened. 
