Well I've managed quite a few more, much to my surprise, but have 5 or six left and a number I don't quite get. I hadn't got the theme, but I think that is because I've got the wrong answer for 5d. I think I have the right answer for it now, which gives me some idea of the theme, but it isn't one I am familiar with.
I haven't got the first letter of 7d, but I can guess it.
I've had problems with 21d which I thought was a maths function and an anagram, but can't find a reference to my answer on google.
I think I may have just got 27ac and 28d, so hints for 31ac and 29d would complete the SE corner.