Do you have a local out-of-hours clinic?
That's how I got diagnosed. My GP couldn't see me for ages, so I took myself to the out-of-hours clinic that my primary care trust operates. I was sent straight to hospital for a quick check up. Everyone was lovely - the nurse at the clinic fetched the Dr, both were very helpful and glad I went when I did. Same applies for the hospital. I felt like everyone was over-reacting because I had no symptoms (except for a urine infection), but was taking seriously and treated quickly.
If your trust operates one its worth going to because levels of 22 - 24 are serious enough to warrant medical attention fairly quickly. And if not, as Andy says, go to A&E.