I feel unmotivated and hopeless about the future, have periods of intense sadness, problems with self harm and thoughts of suicide, can you help?

See a psychiatrist: You are describing typical symptoms of depression. You should talk to your family doctor or see a psychiatrist. Do not wait. Your symptoms could get worse

Get help ASAP: The feelings you describe can seem like there is no way out of it - but there is hope & help. I don't know the resources in the UK, but here in the States there are low fee clinics, crisis hotlines, other resources where someone feeling like you are can get help. There's probably similar help where you are. Do a google search for your locale to find the help you need. It is there.

DEPRESSION: Get an evaluation from a psychiatrist to help identify what depression means to you and whatever else may be bothering you. Consider recommendations for medication if any are given. Get a referral for a reputable psychotherapist to speak with. Meds and therapy combined are most optimal; no just one or the other.

See someone!: What you describe is not just the usual ups and downs of life. When you feel like harming yourself or consider suicide, you really need to seek professional help. Call a suicide hotline or go to an ER if you feel like ending your life. Otherwise, talk to your doctor about referral to a therapist and/or psychiatrist. I'm glad you reached out. Take care of yourself and get the help you need!