Hi, I'm thinking for getting Business BT FTTC, is it possible to get the line set to Fast Path?
Not possible. It isn't possible with any Openreach based FTTC regardless of provider.
Providers can only choose the DLM policy. They can't pick interleaved/fastpath etc. The DLM determines that on its own.
If it's a Huawei cabinet then G.INP will be enabled on the downstream by default.
If it's an ECI cabinet then who knows. It appears they resolved the G.INP issues but I'm not certain it's enabled all round.