Just to reinforce what others have said, you don't have a real problem. What most people call a router is a modem/router, the modem bit scrambles and unscrambles data to send it outside the house, the router bit distributes within the house either by wifi, ethernet or both. You only want one bit of kit acting as a modem.
As far as I know, the BT kit only works if it can see BT at the other end, its locked down much as a mobile phone is often locked to a provider. County Broadband (CB to stop me having to type it out too often) have come to our village (more on this later) and they do provide a modem/router presumably with ethernet ports so you can just plug your house end cable into it. At the other end you will need something, either a cabled solution or a second router. You can often reconfigure old modem/routers and tell them to be just a router but there are lots of generic solutions. By putting the cable in you have done the hard work as long as the new CB installation is close to where it is.
I am with Zen and use their supplied Fritzbox modem router, the house is L shaped and the garage was out of range so I bought (outright, not added to contract) a Fritz mesh repeater. The main unit is downstairs at the back of the house, the mesh repeater upstairs at the front, and between them I get good wifi throughout including workshop/garage and garden. One plus is that I can sit in the car and put destinations into google maps while still on wifi - mobile signal is rubbish here. I could have got any generic repeater, I went with the same brand as the main unit because its a seameless transition - phone etc connects to the one it wanst with no need to do anything - and things like configuration changes I make or firmware updates all mirror on both boxes at once.
Until 2 years ago I got phone from BT and broadband from Zen. I bundled it all with Zen, considerable overall savings, keeping the same number. That was seamless, as long as you are out of any contract lock-in with BT. The new provider does it all and tells BT for you, BT send you an 'are you sure' email to stop anyone simply taking your number without your knowldge, but it was much easier than I expected.
I also have an old but still fine TP link, ethernet to modem/router, data over power lines to the other end which is cable into TV. Its in an odd corner and even with the repeater upstairs the connection could be flakey - the TP works and I never have to think about it.
CB have a mixed reputation here, they came and did a pretty hard sell and sign up early incentives but were well over 12 months late delivering anything. People with straightforward connections seem happy enough but there have been lots of problems. They said they would use (and have licence for) existing BT/Openreach conduits and poles but often didn't. I found a guy looking at the sky in my garden, asked and he said they would be putting a pole on the track behind the houseand running a cable above to access the houses behind. I asked him why, as they had dug up the track and put cables in 3 montsh before. He grunted and went off, left hand/right hand. A nearby neighbour can home from a week away to find a pole in the middle of his lawn, after much fuss they took it away and did the job underground as promised. Another neighbour had an install, hole in front of house, old copper cable was through side. CB will only put in 3m of their cable inside the house, so he is now runnning his modem on the floor in the hall using an extension lead unitl he sorts it properly. It probably depends on who turns up on the day and how grumpy or helpful they are - looks to me like they use subcontractors a fair bit. We know people still waiting for promised connections, trees in way and suchlike. I think an underlying problem is that the people who sell (and are doubtless incentivised) have a quick look and say yes we can connect you, when the trench diggers, pole hangers and actual install engineers come (not all at once) they find difficulties and it seems never talk to each other. The house attached to the local pub signed up, domestic not business, but now long after the 'sell' they want c £3k connection fee for some reason. So probably an equal balance of happy and unhappy but reputation is clouded. Once its settled down hopefully their reputation will improve.
I stayed with Zen, FTTC and I get a real 70+mbps because I am close to the green box. That lets me stream 4k TV and do lots of other things with no issues so its all I need. So why not CB? I wanted to see how others got on first, I stlll do some self employed work from home so a bit risk averse. Their introductory offers are just that - the headline numbers are what you pay for 6 months so any saving is trivial over the likely life of the service. With Zen I am paying £42 ish a month including line and phone, CB full price basic speed including phone would be c.£54, not much different but I don't need it - maybe one day. Zen have email servers which is convenient, I can authenticate and use them for my business emails (I don't have ISP dependent addresses), CB don't - its just connectivity is I would have to find another solution, all possibe but why? I don't much like CB terms - minimum 2 years then rolls over into 12 month contracts unless you cancel: with Zen I signed up for 12 months (long gone) and it then becomes a rolling monthly notice period. Other things I buy into, like mobile phone, have an increase formula (rpi+) which we might not like but is understandable, CB can put prices up at will. They are the only provider who can use their network (as with lots of others I know) so as soon as you go to them BT can reallocate your copper wire slot and you are stuck with CB forever. They are a new, smallish, company with a lot of investment funding from L&G and who get big Government grants for rural broadband roll out (they put a connection box at the edge of our property, unasked, I bet they get paid for that) and didn'y or couldn't answer questions I asked at a presentation about their 'back end' - what 24/7 support do they have. It may be fine, if it is why not tell your sales team. So too much uncertainty for me at this stage. But admittedly that's just me: something of a pessimist and wanting to keep optiosn open until the heralded great copper turn off whenever it happens.
So - sum up you don't have a difficult problem with phone or on the 'inward' side. For CB I suggets you dig deep in their website, see of your install would be within their connection specification, length of trench etc., and if you are happy with their T&C. If the answer is yes, you should be fine. If there is anything unusual about your location, suggest you get answers by email and keep them.
dumping the landline as well ). I did ask the provider Alncom which modem/router they use and recognised the brand but have forgotten, they also said that they would provide an extender foc if I needed it to access wifi in the garden - I do.
