Well ive found the solution (good try MS - but hah!).
ALL the accounts had been locked out?!! (I didnt realsie the graphic login list-view removed a user from the list if locked out, but there you...

Just installed family safety, rebooted - no accounts showing to login!
ctrl alt del to nt login - entered password for my account, said was locked out! Logged in with admin account, went to user...