Well it had to happen, went for a drive and dropped the front offside wheel into a pothole, I winced but the car seemed alright, but a couple of miles later on came the light and air suspension fault. I dropped the car into my local garage, up on ramp and you could hear the air escaping plus a 1/2" tear in the rubber, new struts needed.
After searching the web came across this firm Jaguar XJ or on ebay Jaguar X350 XJ6 XJ8 XJR Rear Air Shock Air Strut Air Suspension Damper | eBay
They were'nt delivered next day due to a mix up in addresses but they arrived fitted straight away and are fine. Returned old shocks and got my core deposit back, really pleased with them. So if someone wants a cheaper option try them.
The difference in ride quality is quite noticable, how many cars are out there riding on deterioating suspension struts and not getting that floating on air jag experience.
I have no connection with the above firm.

Regards Keith

 

From looking at their website, I reckon they are doing in the UK what Arnott did in the US, namely fitting a new air suspension diaphragm, and for the rear unit, a new lower bush.

Essentially this is a bit like replacing a broken coil spring on a McPherson strut. Provided the damper is OK, (no leaks etc) then this is a perfectly satisfactory repair. What I'm not sure about is what happens if there is slight leakage at the top seal. We know that over time, the top seal (a large rubber moulding, can start to leak around the edges. This leak is very small so unlikely to overwork the compressor. They may, of course seal the top.

All these Bilstein air spring units have a valve in them that retains about 3 Bar pressure in them to keep the diaphragm in its correct relationship, and avoid twisting.

Uesful to know about, so I'm going to bookmark these people. New OEM Bilsteins are also now available at around double the price. Of course our 20% VAT doesn't help matters !!