Hard to say... From your description, it could be as trivial as a faulty connection between the laptop and its display - perhaps as simple as reseating a connector - or it could be a faulty display. Given that a PC repair place will probably have a minimum charge of somewhere north of £30, I'd say you were looking at anywhere between that to re-fit the connector and £200 to replace the display if that turns out to be the problem. There's only one way to be really sure, and that's to get it checked out.
What is Amazon Go and will it come to the UK? The store without checkouts or queues