I'm in the US, and I think it's usable. I like
Lennon too; I'm not sure which I think is better.
Lennox reminds me of
Mary Lennox, and
Lennon reminds me of (who else)
John Lennon. I love
Lennox Peter. I'd probably call a
Lennox Len or just
Lennox. Maybe Nox. Not
Lenny though.