From how you describe it I would suggest that it is the repeaters (the extra boxes) that are causing the problem if the Broadband connection can actually make it as far as the first box in the house. BT will probably not show much interest in the wiring beyond the initial box. I would go back to whoever did the extra wiring and ask them to come back (under warranty) and demonstrate the full functionality of what they have installed.
At first I bought records, then I started to collect records; now I merely accumulate records.
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