1. NHS Choices
The Mental Health Foundation does not have an advice line, but its website has a lot of useful resources which can help you understand mental illness and how to cope when the good times go bad.
For example, its website has a guide called "How to Talk to Your GP About Your Mental Health", a booklet on how physical fitness can benefit your mental state called "Let's Get Physical", and "Mental Health on the Go", a short printable guide full of useful details that you can fold and put into your back pocket.
Also, visit this page for wellbeing podcasts and tips on looking after your mental health.