Just a hint for anyone else, checked alternator belt against old ones. 1 cm longer at 810 cm was why the alternator fan chewed the Samco hose. Hard to believe.
Old 80 cm belt on and all fine. Took off swirl pot and reverted to standard set up, took return to header hose off and eventually cleared air lock in coolant system.
Strange as never had this problem with umpteen head changes on both my RS.