I see that I'm on the same wavelength as Enigma, so these responses have been most useful.
I'm now stuck on three :
28A - Shelter in bed, close to fire (4)
C?T?
25D - Mount international operation backing hosts (5)
P?N?O
&
40D - The horse requires treeless racecourse, however (4, 5)
T?E? A?A?N
I hope that not many of these letters are wrong!