This is a big document, but compiles a lot of different research about the reasons men are at more risk at committing suicide in Britain. There's no one overall arching reason but a combination of many factors. Hope you find this useful.

TL:DR - Executive summary on page 8.

https://www.samaritans.org/sites/default/files/kcfinder/files/Men%20and%20Suicide%20Research%20Report%20210912.pdf