Revert "Hotfix: flexible iframes on homepage"

This reverts commit 0fc1f4e26a8126559acecd25c28c0f447f67b559.
Revert "Merge branch 'update/videos/youtube'"

This reverts commit 99ea9aa015a92261b21c349a692527d33c6cc546, reversing
changes made to e78914bfc374f5b0d1213e753e2d882b285034cb.
Add additional subscribe icons
Widen central column whilst maintaining line-length
Add new subscribe options to subscribe page