So, doing a "sh bgp ipv6 uni 2400:cb00::/32 long" reveals that CloudFlare are
currently announcing a bunch of /48s to the rest of the internet through
nLayer only - as far as I can see.
Simple suggestion: announce the /32 to the internet from all peering points
like good Netizens and then announce your /48s from whatever peering it is you
want the traffic sent to and tag it with the NO_EXPORT community attribute so
you're not spamming up everyone's tables or hoisting yourselves by your own
petard by getting filtered out.