I am a single parent to 5 (ages 11-19) and DV survivor. I was not born in the UK. So my family like mother, father and siblings are not here to support me in any way.
After divorce and when my children were younger, I did not work. My income at the time came from benefits alone. In terms of doing something for myself: I could not do really anything for myself for 2 main reasons: first, I was on a very tight budget; second, there was no childcare - for me to be able to go out of the house for a few hours and relax. Friends are busy and sometimes I would feel guilty to ask them. Many people, even your good friends may not really understand what single parenting is like day to day.
Now as my children are a bit older and I can go out to work, I may go out for a meal with a friend once or twice a year or just for a coffee.
Going out and doing something for myself is good for my mental health. It is therapeutic to just disconnect from your normal routine in the house. It's refreshing and children benefit from a happy mother too.
If I could something more for myself, I would go to a spa, go to a classical music concert, spend a weekend away even if it's once or twice a year so I can recharge so I can perform better at home and at work.