There's an option of homeplugs that's been mentioned. But that means laying out £25 or so. A cheaper option could be a plug in wifi booster that has an Ethernet port. They're about £8 off eBay. Plug it in by your box, link it to home wifi and connect Ethernet. Change box settings from wifi to Ethernet.
I've used these on openboxes without issue.
https://www.ebay.co.uk/itm/252481287727