As with any DNS provider they can presumably spoof any site they wish too; so I'd be pretty cautious about using them for all DNS calls.
/etc/resolver/bbc.co.uk
with the contents: nameserver 208.122.23.22
nameserver 208.122.23.23
And now you'll be using unblock-us's name servers for just bbc.co.uk and its subdomains. You could do something similar for your entire network with dnsmasq.Thanks for the tip, though, and kudos to Unblock-Us for being one of a VERY few sites that let you trial their service without giving them payment details.
edit: using unotelly.com's DNS for co.uk and bbchdsodsecure-f.akamaihd.net works for me.
server=/bbc.co.uk/###.###.###.###,
ip would be for the alternate nameserver