Whalley Range is most notably the place just outside Manchester city centre, there is also a Whalley Range in Blackburn which is probably where the Manchester one gets its name from as Samuel Brooks, who built the area then known as Jackson's Moss, and was born in or near Whalley in Lancashire.
Anyway I digress. Now most of my Cockney knowledge comes from my dad who was a bona fide cockney and I often heard him use Whalley Range as an expression. Doing a bit of research it is possible that this isn't cockney rhyming slang and a Manchester based alternative.
Since most Cockneys never leave the East End and have no knowledge of any places beyond West or East Ham they would not have heard of Whalley Range so wouldn't have known of its curious use as rhyming slang for change. I have of course slightly exaggerated that, Cockneys do occasionally experience other parts of the world, I believe Peggy Mitchell is currently living it large in Spain and she's even been there before.