Broadband in remote location

Hi, I’m new to the forum and not 100% sure how everything works so please excuse me.
We live in a remote location that’s about 4-5 miles from the nearest telephone exchange point. Our phone line quality is poor and broadband speed is about 0.5mbs through the line. There is no sign of superfast anytime soon although I think it’s at the exchange. I’ve looked into a 4GEE sim broadband option which would work and give us about 50mbs speed but it’s quite expensive (over £60/month) and its limited to 100gbt/month. We have kids and they drain it with YouTube kids etc. Is there cheaper options out there am that are unlimited?? I’d really welcome any tips or advice. Thank you in advance