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The article says:
Six fire engines and around 40 firefighters attended the blaze above Cycle Stop on West Green Road at around 7pm on Sunday evening.
My emphasis. I merely speculated about a flat above the shop, but it's obviously likely that that's what the floor above is used for. Equally obviously, it's possible the 'above' is incorrect and that it did start in the shop, but the article doesn't say that.
Where did you see mention of the flat above the shop?
As I said, there were lots of deliveroo bikes in there so battery fire isn't that surprising.