Only Openreach would have that information, as they provide the cabacity for all providers.
The best thing to do at the moment, is to place an order for a phone line. Once that is working, then place an order for broadband.
There is not much you can do. What speed do you get with normal broadband, as that tends to be more consistent on download speed compared with a FTTC connection, especially if there is heavy demand at peak times?