All complete bar 2, which no-one else seems to have had a problem with! But I have.
15d: "Transmission of ennergy taking root but not the speed of light" (9) r?d?a?i?n Must be radiation but how on earthe does this fit the clue?
13d: "Star position of the capital in Oman" (7,3) ?e?d?n?m?n