Let me look into my crystal ball...
..it's rather murky and dim.. oh wait, the mists are clearing. I see.. you're going to get.... an examiner calling your name. This person is holding a black bag. You're being given a pen and you're writing something down. The crystal ball is misting over... oh dear, the spirits are not talking to us today
Seriously, though.. it's impossible to predict exactly what you're going to experience on the roads. Whatever you do get, it's only the same as every other driver on those roads are experiencing at that time. Yes, the roads are likely to be busy at 8.20am, but the route will be carefully chosen to avoid the worst pinch points so that you'll be moving as much as is possible at that time. As for country roads, that test centre isn't far from a road which resembles a country road.. it depends on your definition really. If you're taken north, the road goes uphill, past an ambulance station and enters a 40 speed limit before the road starts to bend and a 50 limit with double white lines are in force. It looks as close to a country lane as you're going to get round there.
As for what examiners will be doing.. once they've signed you up, they'll ask you to show them where your car is parked. Before getting into your car, they'll ask you to read a number plate from a distance, then if all is well, you walk over to your car where two vehicle safety questions will be asked. Once in the car and settled down, the examiner will explain that you will be driving for about 38 to 40 minutes and will experience various roads and traffic conditions. You'll be asked to complete two reversing manoeuvres and possibly an emergency stop, the sort of things you've been practising with your instructor. Throughout the test, continue ahead unless traffic signs direct you otherwise, or if asked to turn, which the examiner will do in plenty of time. From then on, simply follow the examiner's instructions, following the rules of the road and your instructor's advice and you should be fine.
Providing you're properly prepared and don't have a brainstorm mid test, you have every chance of passing.