Hi @Ian Clark ,
As Ordinance Survey (OS) provides these tiles directly for free to consumers, I recommend reaching out as I mention in my prior comment as you can leverage these tiles yourself without Bing Maps. My team, Azure Maps, support the Developer Experience and Software Developers can add OS as an independent layer to Azure Maps and Bing support is not required for this to occur. You can look at https://samples.azuremaps.com/?search=tiles&sample=tile-layer-using-x%2C-y%2C-and-z as it brings in a third-party tile set from Open Street Maps (OSM) and you could do the same for OS tiles.
To give feedback to Bing on their decision, use the "feedback" option within the consumer experience rather than within the Developer Forum.
Sincerely,
IoTGirl