Miles,
The human animal is pretty tough. We evolved eating meat that was full of bacteria. For millions of years there were no refrigerators, freezers, canning equipement, or chemicals (other than salt and there is controversy to whether we used salt at all). In short, we hunted and killed animals for food. We dressed them on the ground with wooden sticks and crude stone tools. Within hours the warm meat would be swarming with bacteria. This is the way of life for all animals in the wild. Their food, whether plant or animal based, is not aniceptic. Many here make and eat "high" meat, which is just meat that has been allowed to grow lots of bacteria - in otherwords, it's slowly rotting.
I do keep the bulk of my food frozen. I defrost and prepare about a weeks worth at a time and store it in the refrigerator. Early in the morning I pull out the days portion and let it warm up, often for 10 hours or so, and sometimes in a hot car, until I'm ready to eat it. By the time I get around to eating it, it is often full of bacteria as evidenced by a rather sour taste (which I actually have come to enjoy). Most of us were initially concerened with bacteria and parasites, but after a few weeks or months we found we didn't die nor did we even become sick and so we just stopped worrying about it.
I eat organs as part of the pet food I add to my food mix. I prefer to get a wide variety of organs and mix it with regular muscle meats than to eat individual organ meats separately. Either way is fine as the people who eat whole organ meats are doing great as well. My way is just my preference. About 10% to 15% of my total meat intake is from organs. The rest is fat and muscle.
Not sure why you are concerned with toxic vitamin overload from eating organ meats. I know of no such case ever happening on a paleo style diet. Usually you get to the point where you just don’t want anymore of whatever food you are eating long before vitamin toxicity sets in. As an example, you might get to the point where another bite of liver and you think you’ll vomit, but kidney, heart, spleen, muscle meats and fat all sound great. Your body knows what’s best and will not let you overdo it unless you ignore it and force yourself to go against how you feel.
Organic is a total waste of money. It is totally meaningless as there is no standard definition for it. Feedlot meat is by definition “organic” if the animals ate organic grains (whatever that means). This doesn’t make them any healthier.
There are several grassfed meat producers here in north America and they are easily accessed on the web. Just Google “grass fed meat” and you’ll get dozens of hits. The UK and Europe are a different matter. Maybe Tyler can help you there since he is in the UK.
Lex