Green’s Dictionary of Slang

blimey! excl.

also bligh! bli’ me! blime! bli me! blime me! blimy! bloomey! bloomy! blue bli’ me!
[oath ‘God blind me!’]

an excl. denoting surprise or disbelief.

In exclamations

blimey Charlie! (also blimey Joe!)

[20C+] (Aus./N.Z.) a general excl., used as a sign of the relief of nervous tension.