[bitfolk] IPv6 reverse DNS

Hi all, I'm a bit confused by this, I suspect, because I'm more used to setting this up with IPv4 through nice, easy to use control panels! I want to give my VPS's IPv6 address a reverse DNS entry. - DNS for my domain is provided by 123-reg. - I can see in the Bitfolk panel that I can delegate RDNS to various name servers. - 123-reg don't offer the option of PTR records in their control panel - I can see how to make zone files here http://rdns6.com/zone Am I stuck if 123-reg won't let me create PTR records? Can I use the bitfolk panel to delegate to a completely different name server? Would there be a problem using my VPS as the name server? There's probably a fairly fundamental gap in my understanding so any pointers would be appreciated. Thanks Alex