John,
If you're south of Gatwick, you may find Gumtree at Ditchling Common helpful. I had mine down on the bumpstops, with a hard fault, so I pumped it up manually (jumping connectors) as they couldn't do it 'til the next day.
I drove it down there and they read/reset it while I waited - they reckoned a front height sensor was out of range, probably caused by a pothole, and recalibrated it. I think they charged me £30.
While he was at it, he checked my compressor (by putting his thumb over the filter port) and advised me it was quite weak. I thought about changing the seal, but bottled it and bought a rebuilt LR compressor (not from Gumtree). I will replace the seal on my old (now spare) one, though.
Years ago I had an old Disco and had a couple of dealings with Gumtree (then at Plumpton) with that - but mainly just picking their brains. The only 'work' they've ever done for me was my EAS reset, but I think they're pretty knowledgeable and helpful.
Might be worth a shot for you in future.
Rod