Genetic Testing

Background: I'm the eldest of 11 siblings. It is now known that four (two with the same father, two with the different father) have a condition called phaeochromocytoma (cancer of the adrenal gland). One brother recently had a tumour removed. One other has had a genetic test and it said that he will likely develop tumours at some point. The other two, I'm not so sure (the reason it's taken so long to collate all the information is because all four are adopted, two to one family, and the other two to a different family, I'm in direct contact with all four siblings though).

In April, I went for a test, but it was not a genetic thing. It was a blood test and a 24 hour urine collection. Both came back fine. I thought that was the end of it.

However, since the condition is almost certainly passed from my mother (since the four affected siblings do not share a father), I am now thinking that I probably need a genetic test.

Does anybody know how this is done? Can I just go to my Doctor's and demand one? Since this condition is very rare, I am wondering if it's worth trying to find out who my brothers specialist is (in Southampton) and contact him, as it might be better to have the same doctor monitor all of us? I don't know if that's possible, as I live in York (my brothers deal with Southampton hospital as they live on the Isle of Wight).

If I go privately, is such a test very expensive? Has anybody ever had one?

I'm now 25, and I would have thought that if I was going to become symptomatic, it would have happened by now since all four affected siblings were diagnosed before the age of 18. Nontheless, it's now a concern and I would like to rule it out (or not).

Any advice appreciated.