Air suspension

Both sides of the air suspension on my S2 Discovery are deflating over a period of days now, so I guess it is time for new air springs. These have never been changed in the 8 years of my ownership, and who knows if or when they were changed before when I bought the vehicle at 89,000 miles? There are no codes stored on the SLABs so I guess other than that the system is OK, as it works as it should, it just goes down over a period of 5 days or so.
However I should like to ask a couple of questions regarding the job.
1. I am thinking of supporting the chassis with axle stands and use a jack under the rear axle for removal and inflation stages.
2. Depressurising the SLS system. Can this be done from the Nanocom? If so I am not quite sure where to find this facility. If not what is the best way?
3. The old bags have screw in fittings. Is it best to remove the top clips and drop the bag slightly to get a spanner in to remove the air supply line?
4. I am going to replace them with RKB101200 P Dunlop bags, but they are fitted with a push fitting, is it just a matter of cutting the old 12mm screw fitting off and pushing home the bare air supply line into the new bag?
Any other hints and tips greatly appreciated as I have never done this particular job before.

I replaced mines one at a time for each side using one jack only, as they were also very old i just stabbed the bag with a knife when the body was lifted then cut the pipe near the olive replaced the bag and pushed the pipe into the new fitting(just concentrate to cut the pipe straight)... took me max 15 minutes/side (removing/refitting the wheel included)

if you want to be scrupulous to deflate them with nanocom go into "utility - sls calibration" and there you have the "lower" command for each side but you have to do it more times as it deflates just a bit each time

I deflated by opening the compressor box and undoing the air unions to each side. Support the chassis on stands and yes i used a jack on the axle although its not necessary really. Not a hard job

Today I changed the air springs and just thought I would complete this thread with a few findings.
Support.
I jacked the tow bar and stuck an axle stand underneath it for the body support.
Raising and lowering the back axle gave me access to remove and refit the air springs which is surprisingly easy.
Deflation.
I used the Nanocom to remove most of the pressure then drilled a hole in the wall of the spring to extract the remainder
Old and new air springs
The original old air springs were Contitech, the replacement were Dunlop. Dont get confused by the different lengths of these two.

Air fitment.
The Contitech uses a screw in adapter, whilst the Dunlop is a straight push fit. The old screw in adapters can easily be removed by pulling the top of the air spring down and a suitable spanner can then be engaged with the nut. Just remove the old adapter and cut back to a clean undamaged portion making sure as Sierafery mentioned that the cut is clean and straight. There is a raised portion on the tube that you can engage a pair of long nosed pliers against to push the air tube fully home.

Testing
Start the vehicle and ensure the air springs inflate and operate cleanly. Drop the vehicle to the ground on its wheels and run the suspension from max to minimum height using the Off Road switch and if you have it a rear trailer tow bar dipping ability. Road test, ensuring the suspension returns to normal road level at 18 mph and the Off road light extinguishes on the dash.
Result
Who knows. I will have to wait and see if this has solved the deflation problem.

The problem is solved, everything working OK on the air suspensoin with any more deflates