I thought i would add my experience to the search engine so it may help others in the future.

After my air con went warm i contact a mobile guy for a re gas.
He duly turned up, supposedly pressure tested it, and re gassed with dye.
It lasted all of one hour and i called them to ask for a leak detection.
A week later he came back and after a while said it was coming from the compressor area but said he was unable to help any further.
He recommended a place in North London and said be prepared for a bill of £1500 as everything needed to be stripped for access.
I booked it into a local LR indy that i've never used before expecting the worst.
After his own diagnosis he called to say a hose had split near a bracket and it will be around £200 plus re gas.

Thats more like it!!

If the hose was split on vacuum down then it would have shown up then. I would not use him again.

They showed me the pipe, it was the one you suggested.

They said you could hear the leak it was so bad.

The original mobile guy had good reviews on this site!!

I don't see any "hoses" on my system. The pipes are all metal. I wouldn't have thought that a rubber hose could cope with the pressures involved.

I guess these things get lost in translation sometimes though.

You are correct, it was a metal pipe.