OK, thanks everyone.

The regs about putting cable next to insulators
are explained in Newnes, but I will
have enough room in the ventilation space between
the insulation and sarking for cable.

Hmmm..... can I put junction boxes in that space?
It will be venilated at eaves and a through-roof
ventilator, so condensation should not be a problem,
but it is one more thing to worry about...

Thanks,
David P.