Once the BT service is activated, it should work. The phone line has to be activated first, then the broadband. You should not need a visit.
If everything goes well, when you move in, it will all just work. However, you should allow up to midnight for everything to be turned on as sometimes things need updating at the exchange.
You might need an engineer install if you're transferring Infinity. But they usuallly don't bother these days.