Newt sorry I dont agree with you on this.
Obviously it costs BT more money to provide broadband to a remote village than it does to a city.
But for several years that cost has been subsidised by city dwellers hence most services having the same price regardless of location, BT pass on cost savings to isp's for the big areas to isp's but most isp's choose to use it to subsidise people in areas like yours so basically people like me pay more so you can pay less if that makes sense.
Plusnet is the odd one out in this instance, they chose to not subsidise and hence they have regional pricing. Your MP will get nowhere, ofcom will 99% chance tell you to choose a competitor instead who subsidises your area.
As for moving your line not only will openreach say no, it would also be a very bad idea, a longer line will suffer more problems, especially on performance.