we know personally about one user who licensed charts
from Admiralty under Windows. No issues at all. Worked out of the box.
At bit surprising as he came with the whole DVD/CD set from UKHO/Admiralty - seems that Admiralty works this way - and finally used InstallPermits for three cells.
Anyhow the S-63 plug-in works under all architectures and you can license
from different resellers. Admiralty is one and works ok.
When you license
cells/charts be aware about the different license periods and hence different costs. After expiring the charts are still at hand but you won't get any updates anymore.
We have direct relations to Chartworld.com at this moment and no feedback from UKHO.
More information at the S-63 gateway for OCPN at o-charts.org