Looking for an adult diagnosis in Central London

Hi - I am very late in life looking for a diagnosis but feel it would help with closure and future treatments, as things aren't going great, have been round the treatment circus a few times and my latest therapist suggested that a diagnosis could help.

Having trouble finding a clinic that will do adult diagnosis and help/referrer for any aftercare that may be necessary. Can anyone give any recommendations? Read some very negative reviews about some clinics - would like to hear from someone who's been through the experience with a positive outcome.