I asked a motorbike mechanic about the WD40 damaging the chain O rings, his response was "utter rubbish mate!"
I use the Asda cheapo WD40 copy - spray on and whizz chain through the chain cleaner brush - clean off with a rag, repeat.
Once chain is looking shiny and clean, apply the chain lube, generously, leave for a few mins then wipe the excess off and job done