It was as simple as put the more powerful 98/99 RON jungle juice in the tank, also it has taken away a lot of the dieselly noise.  So much so that I can no longer hear ir in the cabin!  Happy days

Okay so maybe not completely cured    It certainly is improved, used to go between 75 and 90 depending on the road and speed.  In the first few days after filling up with the stronger juice it went to 90 and stayed there, now it has started to fall back to 85.  The dieselly engine noise has definitely disappeared though!  How long this lasts ? Who knows! :|

Edited 7 June, 201511 yr by SkodaKitteh