well.... what I will say is this:
I got the pipe off, with help from my brother, using a very long extension, ratchet and a universal joint with the correct size socket on the end. Using this method removal of the banjo bolt / union was very easy - re-fitting not so much. Predictably the copper washers were a nuisance to try and re-fit.
With the pipe off I used my nice compressor, shoved an air-gun in one end and my brother grabbed the other end. We found the leak my submerging the rest of the pipe in a tray of water and following the bubbles. It wasn't a big leak but with the pressure of the PS behind it I am not surprised I was losing a fair bit.
Still the , we wire brushed, light sand and de-greased the affected area, applied chemical metal and re-tested using the above water dunk - no bubbles.
I'm off to take my 159 for MOT now so wont have time to re-fill and test before I go. I will give it a try when I get back from MOT and fingers x'd no more leak.
If that is fixed then its on to replacing the exhaust mounts and undersealing the floor pan.
1999 156 1.8TS Sport Pack 3
2001 166 3.0 V6 24V Super
2003 156 GTA 3.2 V6 24V
2005 156 1.9 JTDM-Jet Sport
2008 159 1.9 JTDM Lusso
1997 GTV 2.0TS Lusso
2001 147 1.6TS Lusso