Thanks for all the help. I bought some proper hydraulic hose and some decent jubilee clips. I cut out the old compression fitting, that you can see in the picture. Cleaned up the metal pipe then fitted a piece of the hydraulic hose and tightened the jubilee clips, until they wouldn't tight no more but the fluid was still sprayed out. So in the end bought a 10mm water compression fitting from screwfix and tried that. It seems to be working, just got loads of air in the system so go to get it out. I was looking how the pipe routes, it looks like the radiators have to come out, to allow the complete pipe to come out from both sides. Or is can it be removed without removing the radiators, so I can get a new one made at a hydraulic place?
Thanks again for the help.
Addy