Can anyone recommend an injector in the UK skilled in correcting/revising lip filler?

I had my lips dissolved 1.5 years ago and I’ve had four sessions of lip filler since, none of which have worked. My top lip can no longer hold filler in certain areas (it disappears pretty much immediately after the appointment) and I need an advanced injector who can work on the structural issues I now face with my lips. Any suggestions? Many thanks!