A couple of thoughts:
Your outgoings are already very low. I don't think you can cut these, really.
I mean, sure, you could move to £5.99 Netflix instead of £10 Netflix. A saving of £4 PCM is still a saving, but it's small fry and isn't going to make a massive difference.
Your Internet seems cheap.
My only thoughts for outgoings is rent. You said your son moved out two months ago? Does that mean you have a 2 bed? Could you move to a 1 bed? Would that save you anything? Not necessarily doable with moving costs, deposit, etc. Just an idea. £750 is quite cheap for rent these days anyway. So perhaps any saving would be negligible.
Is that part of the reason you're struggling now, rent increase, and no more contributions from your son?
Obviously, it's worth applying for Universal Credit.
But the biggest issue is that you only work thirty hours. It's hard enough for people to survive on one full-time minimum wage income, but yours isn't even full time.
I think you need to be more proactive in this area. Lots of your answers have so far been combinations of "no full time jobs," "experience needed," "what's that? How do I get into that? What do I need for that?"
You need to do some research (googling). Get your CV sorted. And apply. Keep applying. PP's are right there must be plenty of minimum wage jobs you can do that require little to no experience. And if you've worked all your life in retail, then you'll have plenty of transferable and customer service related skills.
I know the job market is tough at the moment. (See my username!) I've been hunting since February for jobs and only now have one - due to start in September. You just have to keep at it.