…what % of that roughly 650k diagnosed [in the US] has access to healthcare (it's one thing to be diagnosed, another to have coverage)?
If you believe the statements emanating from Washington, the answer is at least 95%, starting in 2014.
In the big-5 EU countries (where the addressable market is roughly the same size as in the US), the percentage of patients eligible for reimbursement should be 100% in France, Spain, and Italy, where the governments negotiate pricing prior to product launch. The reimbursement situation in Germany and the UK, where the governments do not pre-negotiate pricing, will depend on the prices set by the vendors themselves.