Its weird eh Derek.
I've searched a bit more and got even more conflicting information now
I've asked autolamps whether the H1 HID bulb will fit in the H3 base and ensure the correct bulb depth/focus, especially given this was the kit they supplied to the 996 owner.
Oh, and when I rang P&H to ask they told me botrh were H7 fittings...
I'll check tonight anyway to be sure.