One of the best ways you can improve your pronunciation is to regularly listen to native English speakers who speak with a clear and are easy to understand accent. Observe them carefully and try to mimic their sounds. Below are links to videos of British newsreaders and journalists who speak RP in some form or another.

 

George Alagiah

 

 

Katty Kay

 

 

Mishal Husain

 

 

Sophie Raworth

 

 

Fiona Bruce

 

 

Michael Buerk

 

 

Emily Maitlis

 

Mary Nightingale

 

 

Kate Silverton

 

Julie Etchingham