So I have solved the issues, and it was very simple.
I put a call into our local Rotax guy and had a chat to him. His first response was the pressure spring. So that was the first point of call.
I removed the old one, and noted that it was a good 3mm shorter (and a bit softer) than the old one, which is what my Rotax guy said I would find.
Replaced with new spring and sleeve, and now the oil pressure is perfect right through the operations.
PS - A small dip on take off is normal, according to Rotax. But now it stays in the green, and the dip is minimal.
Anyways... Happy!
Cheers
J
