The saga continues...

Initially recompiling bind 9.2.3 without ipv6 seemed to help a lot.

Then it slowed down to 5s + for some domains, which resolve much
faster on other internet gateways.

I tried switching to named (bind 8) which I presumed would not have
ipv6 support in it, but this didn't work (and I specified not to
listen on an ipv6 interfaces, not that there are any).

I updated pkgsrc and compiled bind 9.3.0 (for the -4 option).

Using the rc.d system, it didn't seem to take the named9_flags with it
when restarting, but when restarting manually specifying the -4 option
it now really does work better!

So the solution is to use the -4 option in 9.3.0 as you originally
posted. I didn't have much success with bind 9.2.3 and USE_IPV6=NO

Thanks for your help

Amadeus