Thank you for the tips, I'll start investigating the project, I tend to watch lots of YouTube videos and then go from there!Changing the dryer, if you have a Hitachi compressor, is straight forward. Hardest part will be disconnecting the hoses from the back side of the compressor (intake and exhaust hoses), and re-installing the compressor bracket when you reassemble due to a hard to reach bolt that need to be tightened. Once the compressor is out of the car, replacing the dryer is a Philips screw, twist and pull, install new in reverse order. If you have the compressor out, you can possibly inspect the exhaust solenoid and clear it of any dust. I'd recommend getting the new compressor hoses, there's a kit for the one that goes from the central valve block to the compressor dryer from Atlantic british, as well as some bits to replace the elbows where the old intake/exhaust hoses go if those got mangled during disassembly. Key to disassembly is to push the hoses into their push-to-connect fitting, and only then depress the release ring, before pulling the hose out.
You mentioned replacing o-rings on your front valve block - where did you source your kit, and did you find the o-rings to fit? I got a kit off amazon and the o-rings were close, but not the same, with several being quite a bit thinner in cross section. I didn't feel comfortable using them, so just cleaned the block out and have been having good luck so far.
The intake pipe goes up into the rear quarter area. The exhaust might also, but I'm not certain. You can see a picture of them in the parts diagram here: https://parts.landroverparamus.com/...0l-v8-gas/electrical--ride-control-components, #20 (intake), and #21 (exhaust, with the muffler can).
I did change the front 'o rings and last night I did the rear ones, there's a great video on YouTube (starting with this one for general info - but on a RR Sport
Range Rover Sport LR3 LR4 Air Suspension Valve Block O Ring Seal
So far so good, the sizes seem really consistent.