Is there no one else you can see that will order a colonoscopy for you? That and/or a camera pill is what you need to find out where you are bleeding so you can get it stopped.
I would NOT do the colon hydrotherapy. Those sorts of things--if they even do anything at all--are for people with healthy colons. Because of your bleeding, we know that something is very wrong with yours. You can make yourself a whole lot worse by doing procedures that shouldn't be done on an unhealthy person. You need tests to find out what's wrong with you before you do any treating.
Have you been over to the UC or Crohn's boards to talk to them? They can tell you the symptoms of IBD (which sounds more like what you have) better than a lot of us here can, and maybe there's another UK person on there that can recommend a doctor that will take you seriously.
And yes, you do still need to eat. Eating is necessary for everyone, but especially for someone experiencing blood loss. I would think that red meat is something you need to be eating for the iron. At the very least, try meal replacement drinks like Ensure, Slim Fast or Carnation Instant breakfast. The first two come in soy if you can't do milk, and you can always mix Carnation with soy milk, almond milk or anything else, for that matter. That way you'll at least be getting some of your daily vitamin requirements.