I found myself in the same position aged 18. I had no experience except my compulsory work experience, and only my GCSEs for qualifications. For all I had ‘worked’ from age 14, it was for a family business so naturally they would give me an excellent reference.
Write to charities for volunteer work, and dedicate one day per week of your time to a worthwhile charity. Next, apply for a short college course. Floristry, an IT course, or anything of your choice for which you get a qualification shows you are dedicated to learning. Why not take a foreign language? Arabic, Turkish, and Urdu are becoming more and more desirable as the trade markets around the world shift.
Play on what you are good at. “I have a full UK clean driving license”, “I am dedicated, committed and exceptionally hardworking with a passion to learn” etc. Don’t lay it on too thick but blowing your own trumpet never hurt anyone!
Good luck in your job hunt, I’m sure you will find something soon!