Find a solution for video storage

**Is your feature request related to a problem? Please describe.**
Currently videos are stored somewhere on Sharepoint but the links are going to expire and break from February onwards. We need to find a better way to host video for the site so that it can be embedded properly. Following migration, the old method no longer works.

**Describe the solution you'd like**
- Videos are stored sensibly
- All videos work internally and externally (where appropriate - should all videos be available externally?)
- Ideally, content of older videos is checked to make sure that it is all still relevant / correct

No files, tests, or entry points are named. Start by inventorying the site's current SharePoint video links and documenting the hosting, embedding, and internal/external access requirements. Done means videos have a sustainable hosting approach, working embeds, and an agreed review of older content.

Written by the indexing model from the issue text.