I'm sorry you are feeling so down, but I can understand where you are coming from. I suffered with UC for twelve years, ran the gamut of meds and finally had my colon and rectum removed in a total colectomy with end ileostomy on June 28th.
If you were on prednisone for an extended period of time it really does a number on your moods. I'm not familiar with the health care in the UK as I am in the US. However, first and foremost, try to get the depression under control. Do you have any family members to give you support? Any support groups for people with depression in your area?
You are so young and have your entire life ahead of you, things will get better. Please try to find help. We are all here to give you online support and are all caring people. God bless.