They do exist, Khandro, and they are typically full to capacity. Plus they work very closely with local councils - who are legally speaking obliged to house you if you fall under certain categories (e.g. you are a woman/child, disabled, etc.). This in practice means that single men who are homeless get zero support (or are forever next in line) and are expected to make it on their own because they are considered better able to help themselves.
Now, yes, that may be true in comparison to an invalid or a child. But the truth is that the existing system for dealing with rough sleepers is not working and cannot cope with them in the right numbers because those services just do not have the amount of accommodation they need - even for those small numbers I posted above.