https://www.slab.org.uk/guidance/private-client-charging-after-a-grant-of-advice-and-assistance-has-ended-what-you-must-do/
If your client wishes you to do further work for them, and advice and assistance has ended, they are free to discuss whether to become a privately paying client. However, to become such a client:
You cannot give your client advice privately while the grant of advice and assistance is continuing.
Advice and Assistance application procedures
This page includes information on how to apply for non-templated increases in expenditure under civil A&A. It covers the information you should provide us with; case-related factors to address in your application; the process for reconsideration of refused increases; the process for urgently needed increases; whether authority for retrospective increases is available; and other guidance you may wish to consider.