yes – David – its an IS 1.5 – the cane creek headset finder gave me the result (see above) which is the same as the Titus carbon frames which the others have had a problem with. It is not an ISi.
Basically the frame comes with an IS integrated tapered headset. The top I can keep but the bottom I need to alter to use a 1-1/8 steerer. So above will slot into the bottom IS 1.5 but reduce to 1-1/8 internal diam for the steerer as it comes with a reducer crown race.