* Don't try to use `ns6.gandi.net': it doesn't seem to work properly.
Specifically, it's rejecting all client requests with `REFUSED'.
* Add `national' as a new nameserver for most of the zones. It's a
reasonably reliable machine, geographically separate from the
existing nameservers, and in a very different AS. I use DNSSEC, so
its less trustworthy status isn't a big problem.
* Add `secondary-dns.co.uk' as a secondary for the A&A reverse zones.
I'm not convinced I can use that with glueful delegation, and it
doesn't currently seem worth trying.