https://www.slab.org.uk/faqs/criminal-legal-aid-if-the-charges-are-more-serious-solemn-cases/
These include:
If you are accused in a solemn case, you are automatically entitled to legal aid while you are in custody, until:
You can choose to use the duty solicitor or your own solicitor. After that you should apply for criminal legal aid – your solicitor will help you to do this.
SLAB only has to consider whether paying your own legal costs would cause too much hardship to you or your dependants.