A small lump of render has fallen out - think it's been knocked by
something. The hole is rather flaky and very powdery, so I think if I
just repair it as it using a bit of mortar, it will simply fall out again.

If this was an internal repair I'd be sloshing on dilute PVA first,
however that's not suitable for outside is it?

What does the panel reccomend I do?

Thanks
David