The FibreNest FTTP is owned by Persimmon.
It's nothing to do with OpenReach so none of the ISP's who sell OpenReach products (BT, Sky, Talktalk etc) would be able to provide you any service over the fibre.
Bearing in mind you could pay as an optional extra to have telephone sockets and they were advertising Sky Broadband
This suggests there's an OpenReach copper line at the property.
If Sky was available to you then any ISP who uses OpenReach's network would have been available.
If an order could be placed with Sky then it could be placed with anyone else.
Someone is telling porkies or confusion has arisen somewhere.
What does the BT Broadband Availability Checker show you?
https://www.btwholesale.com/includes/adsl/adsl.htm?s_cid=ws_furls_adslcheckerIf there is an OpenReach line available then is very likely to be ADSL only