I read stories like this all of the time where patients have to raise a lot of money to travel outside of their country to get treatments. It is a sign of failure in our systems - both the USA and UK. There is a bill in congress called the Conditional Approval Act which may fix this problem in the USA.
In the mean time - wouldn't it make a lot more sense for these families to pool their resources to bring the treatment to their country instead of spending a fortune to go outside their country? For what 4 or 5 of these families raise to get access to a treatment, they could bring the treatment home for maybe 50-100 kids. Our organization, the Musella Foundation did just that with one pediatric cancer drug - for patients in the USA... no reason the foreign charities can't do the same.