My only experience with 123 was years ago, it was disappointing.
They failed to register a domain. Paid a few £ for nothing. Obviously their scripts are buggy.
They are (were) also difficult to reach, if I remember well it was some 0700xx number unreachable from outside the UK and no answers to E-mail.
I am surprised they are still so established even among domainers.
When you pay dirt cheap prices you can expect to get some dirt in return