What sort of new build ?, part of a mainstream development from a large house builder ? , if so did this developer engage with Openreach to install network ( it almost certainly would be FTTP ) or did they elect to ‘lock out’ Openreach and deal exclusively with some other network provider, in some developments the builder limits access to their own network.
In the first instance you really need to speak to the developer if it’s not obvious what telecom provision was made , if OR were allowed to be involved there should be infrastructure already installed ( with new sites the equipment is fitted before the house is sold )
If your new build is something of a one off , like a building on a vacant plot , or a new building replacing demolished one , then that would normally use whatever is in the area , but if the address doesn’t exist in records , because it’s not yet registered with Royal Mail , you may find you cannot get an order raised , and if you do , a survey may be needed as it may not be a simple job to install service, if the surrounding infrastructure cannot easily be used for this new building
