UK ORGANISATIONS WHICH OFFER ADVICE
Here is a list of people who should be able to listen, and to help — though there are no guarantees. These are all well-established UK charities/professional organisations. They exist to offer help to sufferers.
Warning: please be wary of organisations offering expertise on cultism, deprogramming and brainwashing. Some may be more interested in taking your money than in helping you. At the very least, research any such organisation online before contacting it, and ask a professional — such as your GP or a solicitor — for guidance first.
One option might be some form of psychotherapy. (Please note: you don’t need to have a mental illness to find psychotherapy helpful.) Be very careful, however, as regulation of therapists (by the BACP) is not all it might be, and a bad one can be worse than none at all. Or try one of the organisations listed here.