Thanks for the tips guys - the head itself seemed OK when assembled and it went together with new copper washers on the banjos.
The rear bolt and rocker box seem fine and are oil tight - I need to re-torque
the head soon anyway and at least these bolts do not affect that; will consider making a groove for an O-ring.
Took it out yesterday to a local TOMCC event and apart from leaking it got there OK ( only don @10-15 miles ).
Sadly the adjuster rod on the rearset gearchange came away on the way back leaving me stuck in 2nd but I did get a police escort part of the way !