When the Citroen engineers first designed the engine compartment of the CX, the brake accumulator was located in a logical place. It was probably very easy to reach on the first versions of the CX.  But as the CX was modified over time, this ease of access diminished  The addition of airconditioning, a 5-speed transmission, a larger battery, a wider radiator with larger hoses, and under carriage stone guards  all combined to encroach on what was probably an easily reached part.  It's almost as though they installed systems in open areas, with little regard to what other systems they might impact.  So, now, the brake accumulator is a royal pain in the ass to reach, particularly on the Grande Exportation models, which have extra underbody protection that takes forever to remove.  The 2200 had what was likely the original accumulator;  it is seized to the base, it is rusty, and it piddles LHM irregularly when it is turned over, indicative of  a ruptured membrane.  The low location makes it more vulnerable to corrosion from road spray.

It's not just my CX that seems to have problems with unchanged pressure accumulators.  I recently saw a CX at the 2004 Citroen Rendezvous.  The owner had spent a substantial amount of time and money to repaint the car and refinish the bumpers.   But, the accumulator was a big ball of rusty steel.  It was just as weathered and corroded as the frame holding it up.  Obviously it had never been replaced.

Here is the original location of the accumulator bracket, at the forward port side of the engine compartment.  The battery tray is visible at the top of the frame.    Notice the solid layer of grease on the frame!  Grease is good. It prevents rust.    
Here is the aft port section of the engine compartment.  You can see where I have labeled the motor mount (to be removed) the clutch cable, and the existing HP lines.    
Here I have labeled the HP lines that take HP from the brake accumulator to the rest of the hydraulic system.    
I gave the union nuts a good scrub with steel wool and rust dissolver.    
And I installed a new seal.    
Pleaides sells these union - splice adapters.    
I attached one to the HP line on the car.    
I created the new flares with a kit I also bought from Pleiades.    
Here is the new pipe installed at the former location of the Brake Accumulator. I have removed the support bracket for the Brake Accumulator.  This car is a Grande Exportation model, so there is a steel plate under the engine compartment to protect the underside.  If there were not, I would fabricate some sort of plate for this corner.    
same view, zoomed out.    
Here I have pulled the new HP line up behind the rear crossmember, following the same path as the existing lines.  You can see the difference of where I have been cleaning the old dirt and grease    
View of the area behind the crossmember.  I have left the HP line coiled there until I locate the brake accumulator.    
Anchoring the HP lines.  The HP lines should be anchored to the car.     
I used windshield washer tubing, cut it into 2cm sections,
And used rubber-lined wire anchors to anchor the HP lines