Re: Yet another distro?
A dedicated NHS distro doesn't see a big deal to me. e.g. The CERN CentOS 7 distro used by the particle physics community worldwide is more or less done by one man + St Bernard dog. Canonical seem to produce and maintain a full functioned distro on about £85 million per year and I doubt anything remotely approaching that is needed. I suspect the cost would be less than the Microsoft licence fees.
As an indicator of the sort of sums that are ploughed into NHS IT, previous governments found £10bn to spend on the abandoned National Programme for IT system, which would have paid for a Canonical sized operation for more than a century.