I found a place online called Health One Labs that lets you order your own blood work. Well, at least certain ones that they provide,but it's a fairly long list of choices. They have a provider that works for the lab that authorizes your lab requisition and then you just take it to your local neighborhood lab that is contracted with Health One. You have to pay with a credit card and don't take take insurance. I ordered a test for Magnesium levels, Vit D, and C-Reactive Protein. It came to $127, not too bad. I had never known you could do this until David mentioned it in a post. I guess you as the patient get the results, but you can take it to your doctor if you need it interpreted.
Anyhow, I was hoping there was an online lab that does this for stool tests as well. Maybe not. Sending a stool sample to the UK might be a bit too far. Yuk! Maybe I will just ask my GP to order it.