When the cottage was split off from the main residence and made a dwelling in its own right , when the developer made provision for the electric, and water/sewerage they should have also contacted Openreach about communications , presumably they never did .
The way these things generally work , the address pops up on the Royal Mail because the developer did this part of registration of a new property correctly , Openreach use a version , PAF to list all habitable addresses , these are assigned a category Gold , Silver , Bronze , search something like Openreach Gold address to get an AI summary of what criteria are used for each category, yours will likely be bronze .
Something like a bronze address does have a process to get service installed , but it can be lengthy , and some locations are going to be more problematic than others , say (for example) a situation like this , part of a larger property split off and sold , the seller granted access rights over their access road to allow the new owner or visitors to get to the new property but included nothing else , nothing but the property itself was ‘sold’ , basically the new owner is compelled g(but allowed) to use someone else’s driveway and footpath to get to their property, and assume direct overhead cabling to the property is impossible even though telegraph poles are near by , there is no direct line of sight to the building from the pole , or it’s impossible to achieve the necessary height across roads , footpaths, other buildings etc , so a new pole is needed, but it would have to be sited in someone else’s property (possibly the previous owner of the property that’s been sold ) …obviously this builds in delay , while OR approach the landowner with a proposal (that can be refused) or the landowner agrees to a pole but expects more that the normal wayleave payment , so OR walk away , poles are considered the default, say the landowner insists on underground service but doesn’t want payment for it just wants no ‘clutter’ you would be expected pay the difference between what a pole would cost and what the underground scheme would cost, these costs need to be worked out and presented to your provider, who generally passes it on to you , as can be seen there can be a lot of potential issues .
I’m not saying this is the case with your property, it just gives an indication of the potential problems and why the developer getting these things arranged in advance is important and the delay that can follow if they don’t act in advance , new property can’t be sold without water and electricity existing, there is no such stipulation for telecoms .
You don’t actually say which provider it is you have approached , often when people post on here with vague statements like BT/Openreach , it’s because they have no intention really of using BT , preferring to use almost anyone else , but they incorrectly assume BT must be involved so they post here thinking Openreach and BT are one and the same but they are not , many providers only want straightforward Gold type addresses and will simply cancel complicated orders ….is it BT you contacted as there is no such organisation as BT/Openreach , if it were Sky (for example) you would prefer to use , they have exactly the same relationship with Openreach and should arrange anything that BT could arrange.
