London 8:30 hour layover?

In a few days i will have a 8:30 hour layover in london where i need to change airports. I arrive at Heathrow Airport at 7:40 and leave Stansted airport at 16:15. We want to visit one waterstones and have lunch at an Honest burgers. Is this possible? How can we do this in terms of public transportation? Is there... show more In a few days i will have a 8:30 hour layover in london where i need to change airports.
I arrive at Heathrow Airport at 7:40 and leave Stansted airport at 16:15.
We want to visit one waterstones and have lunch at an Honest burgers.
Is this possible? How can we do this in terms of public transportation? Is there another restaurant that is not super expensive that serves the impossible burger? (We want to try impossible/beyond burger)
Thank you in advance
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