There was a psycho therapist Philip Hodson on the radio years ago.
His advice worked for me. So if you are serious about getting to sleep, do try it.
His method with patients was to empty your mind of all activity (the miseries that might keep you awake) by counting as you breathed- counting one two three on the in breath, one two three on the out and then pause one count before breathing in again.
Then he explained eye position. When you want to fall asleep, make sure you are lying comfortably and then close your eyes, and (with eyes closed) turn your gaze upwards. Apparently physiologically that is the sleep position for your eyes.
Then slowly breathe in and out counting as explained above.
His method works very quickly for me - a real knock out.
And since the count of three reminds me of the count as I canter, often just thinking of the horse in canter sends me to sleep. Animal contact is supposed to relax you, so may be the riding image works.
If anyone else tries this, it would interest me to hear the result.