For clarity, we don't build websites for NHS bodies, we build sites for some external organisations that work with the NHS, so logs would be relatively easy if it felt worth it. GA is my only source, but my hunch is that use of blockers is pretty consistent across clients whose visitors are mostly from businesses or institutions, and I see this differential across those audiences. Having spoken to people who work in the NHS Digital team there are definitely pockets of IE use, although it's been getting better - the shift sped up quite a bit after the Wannacry attack.