Updated 16th August 2017
Samaritans - talk to them anytime of the day, in your own way and off the record, about whatever is getting to you. See website for telephone and email details.
Papyrus - Provides confidential help and advice to young people and anyone worried about a young person. See website for details of the National Confidential Helpline - HOPELineUK.
Students Against Depression - has lots of information, tips, advice and self-help materials including a section for anyone thinking about suicide. There are also accounts written by students about their own experience of depression and what helped them.