I agree that the BACP website is a good place to start, but you might also want to look at UKCP and BPC (British Psychoanalytic Council).
You sound like you know what you need and want help with, so you can search for key words - I would particularly look for therapists who mention trauma, or those who have additional training in trauma and or EMDR therapy, which is proven to be very effective for trauma.
Depending on your insurer, you could also search on their directory (eg Bupa). With a lot of therapy being online at the moment, you have a lot of freedom to choose someone who feels right for you, regardless of distance.
Contact a few and you will get a good feel of who might be a good fit, just based on a short phone call or consultation. Trust your instinct!
But definitely make sure they are accredited by BACP, or members of UKCP or BPC as this will guarantee a certain degree of qualification and experience, and adherence to code of ethics etc..