The speaker holes are usually cut next to the strengthening bits as they are too hard to cut!

As ugly as this looks the strengthening second skin is intact and the seat belt mounts are still secure.

In that case I will remove the speakers, as they aren't used anyway, make up some patches for the holes, and zap them in. This thing will never be on show, it's just the integrity I am worried about. Thanks for your help Morris 1100