We just gave our daughter a name which is not brilliant with our surname (alliterative, and slightly rhymey). We really debated over it, but just couldn't find a name which we loved as much. I posted on here (without giving the name), and the general advice was that if we were still considering it it probably wasn't all that bad, and if we loved it to use it.
Our backup name was actually Clara, which sounds fab with our surname, but when she arrived I just knew that she was 'other name'. I'm really glad that we used it anyway, I'd have regretted it if we didn't.
FWIW I think that Clara Ranson falls into the same category as DD's name - not an absolutely brilliant combination but such a lovely first name that I would use it anyway - it is fine as a whole name. She will only use her first name the vast majority of the time anyway.