And when I search for UK connections, that cheap quoted price is via Manx Telecom, not direct-to-carrier (which is, as they say, more reliable). I'd assume their inbound VMNs are, too (which means some networks would get hit with International rates).

There's other complications that they don't seem to handle that well (Text encoding! Bulk sending!). But they may have some luck - their website is easy on the eye, their APIs look sane, and the pricing isn't so bad.