I so sympathise Natalie coz I am also a single mum. I got so desperate that on Monday I took her to the doctor for something else and while I was there I asked for a script for phenegan to get her to sleep. It worked (sort of) - she is only taking an hour or so to get to sleep instead of 2 plus hours. I have also put a cd player in her room and am playing relaxing music to her which partly blocks out the noise of me doing stuff round the house after she goes to bed. And I readjusted our bedtime routine so she has at least 15 solid minutes of me reading and talking to her before she goes to sleep. Plus I stand in the room for 5-10 minutes with my back to her before I ease out.
I hope something works for you soon coz I know just how frustrating and tiring it is, especially when you are on your own