This story seems to not make a whole lot of sense. Here is the basic outline.
First, get your hands on 700,000 used stamps still on the envelope for no more than a tiny fraction of face value delivered to your house.
Second, remove 700,000 stamps from envelopes.
Third, wash the cancellation off 700,000 stamps.
Forth, put them on "greaseproof paper to make them appear as if new"
Fifth, sell £400,000 face value of stamps that have no gum on eBay
"Just over £215,000".
I'm thinking there is a lot more hype than facts in this story.