My name is Dominic Stichbury and part of my practice as a choir leader focusses on getting men singing. I currently run two large men's choirs in central London.
https://www.bellowfellows.com/ Bellow Fellows is a non-auditioned male voice community choir that welcomes men from all walks of life. We meet regularly in central London, there are no auditions and everything is taught by ear. We sing a variety of music, from well known pop to shanties, work songs & everything in-between. You can come along for a free taster in term time - visit the website above or email email@example.com for more info.
http://ww.chapschoir.com Chaps Choir is an auditioned male voice choir that has performed in major venues in London, collaborated with other artists and put on large scale shows. You can find out more about them at the link above. Click on 'sing' for information about membership.
Workshops Occasionally these groups will offer workshops for men to come along and explore their voice. I'll post about these and other opportunities in this meet-up group.