The BBC recently posted a short video looking at the above question (link). The truth is that the terms Counsellor or Psychotherapist are not protected terms and anyone can set themselves up as such.
So what are the safe guards?
Firstly check to see if they are registered with the relevant body, unfortunately there are a few that cover both of these professions, I am a member of the British Association of Counsellors and Psychotherapists, BACP. To be a full member of the BACP you need to have passed a recognised course or sat an entrance exam. In addition to this entrance criteria, some therapist opt to become Accredited which requires a minimum number of hours practise and some addition submissions. Above this is Senior Accreditation which requires further experience and submissions. Although I have been eligible for Senior Accreditation for many years I haven;t decided to go down that route as it seems to offer few benefits to me and none to my clients, hence I am an Accredited, Registered Member of the BACP. National CounsellingSociety, NCS, has a similar entrance system and recognises most of the BACP standards if I wished to join them but my understanding is they are smaller in membership than the BACP. United Kingdom Council for Psychotherapy , UKCP and the British Psychological Society, BPS, are also bodies that you may see accrediting professionals that use talking therapies. Hence the first thing you should do is see who the therapists says they belong to and check the register on the relevant website. Directories such as counselling-directory.co.uk also do this before listing a Counsellor on their site but it’s good to go and check yourself as if that therapist is under sanction for any reason it should show up first on the main awarding body’s site.
So in summary, do a bit of research to ensure that the therapist you go and see if genuine and qualified.
British Association of Counsellors and Psychotherapists BACP
National Counselling Society NCS
United Kingdom Council for Psychotherapy UKCP
The British Psychological Society BPS