I like having an interpreter. My doctor speaks good English, but it's nice to have a second opinion.
The interpreter also books the next appointment for me, and books the payment and pharmacy queues as well.
See the doctor, then just go downstairs, get a coffee and wait for her to bring the queue number.
No extra charge that I can tell. Demanding a doctor speak perfect English makes little sense to me. I would much rather have a scientist than a linguist.