The good news: after a lot of digging around and help from my local garage lift, I've finally found a chafed blue air pipe just after the three pipes leave the wheel well - the garage said that the cause was an electrical connector which had been plugged in between the air pipes and given the location I'm guessing that this is near the low pressure fuel pump which was replaced about 18 months ago.

The bad news: after an Ubuntu upgrade, I can't get my Rave manual to work - could somebody be very kind and have a look - I need the part numbers & routing for both of the blue pipes that exit the compressor (the garage were not happy to patch in a short replacement section) so that we can work out which one to replace and then order the exact part from LR!

Just cut the pipe and put an inline connector in..... Photo to follow.

Edit... http://www.fullfatrr.com/forum/topic15626.html
Page 3 has a picture of the connector in place.
 Previously..
Vogue SE TD6
Defender 90 2.4
Defender 110 TD5
Vogue 3.5 EFI

Thanks for that!

So I'm just searching for 6mm blue air line (guessing 6mm OD and 4mm ID) and a couple of 6mm inline quick fit connectors?

Yip... If you google air compressors, compressed air etc in your area you will find a company that will sell them over the counter. They are relatively common. I used www.compressedaironline.co.uk as they had a local branch.
Are you sure just one connector would not do? Is the pipe damaged along a length or just one spot? Previously..
Vogue SE TD6
Defender 90 2.4
Defender 110 TD5
Vogue 3.5 EFI

The pipe has worn through in just one spot, so I'm juggling between putting a complete replacement pipe in or just a short section to replace the affected pipe (with two inline connectors).

The complete replacement part is LR018434 "pipe - air inlet"nwhich comprises all 3 air hoses from the compressor.

I too hit the minimum order quantity for local suppliers (30m roll of air hose and ten connectors) - but was more worried that most of the inline connectors that I could see online had a maximum pressure rating of 8-9bar and I'm not sure if I have the 9 or 11bar suspension. Therefore I chose to replace the whole air line (hoping that it's the shorter one, not the one going to the front of the car!).

Replacing the complete line looks a bit of a faf compared to the inline connector route, but if you are not sure the connector can handle the pressure then for peace of mind it's the way to go. My problem was an original fitting from landrover failed, so the fact that they use inline fittings must mean they are available.
The part you purchased from dan, does it come with any fittings or is it just hose? Previously..
Vogue SE TD6
Defender 90 2.4
Defender 110 TD5
Vogue 3.5 EFI

The part from Dan is the three preformed air lines with the rubber grommet attached which fits into the wheel well. I'm hoping that the leaking hose is the shortest one - but I was in the car up on the ramp keeping the compressor going so that they could find the leak and so did not see which one it was!