How to know the speed zone of the road- UK

So I have my driving test tomorrow, in a manual car. One of my biggest problems is that I don't know the speed zone of some of the roads I ride on, and hence don't know to go 20mph or 30mph. I understand if their are parked cars on both sides of the road, then the maximum speed is 20mph, and I understand when there are street lights on both sides of the road, the maximum speed is 30mph. But some roads don't have any speed signs. Whenever I enter a new road, there tends to be a new sign telling you the speed zone of that road right at the start, but some roads don't have this. My instructor has told me that if you see no speed signs, just assume it is a 30mph road- she also said that for 20mph roads there is usually regular signs on the road with "20" on it. So any tip that would stay with me forever ?

I understand if their are parked cars on both sides of the road, then the maximum speed is 20mph,

A speed limit is a maximum, not a target.

But you could get minors for going too slowly, because it can be dangerous, it's best to stick close to the speed limit, unless the road conditions make it unsafe.

That's correct, any road with street lights and no other speed signs is 30mph, any other speed limit would have repeater signs at regular intervals.

What if there are street lights and also parked cars on both sides of the road?
Edit: Never mind, someone above already answered it

Great posts from Doones.

I'd also add that a big part of passing the driving test is "observation". Where you look at what's going on outside the car and respond to it.
When learning to drive a car, at first you will miss a lot observations because you are too focused on the mechanics of driving the car.
As you get better, the control of the car should be as automatic as the control of your body as you are walking down the street.
At that point you should be taking in ALL road signs as well as general road conditions, marking, layout and what other road users are doing around you.

Another point is that the Sat Nav system used on your test, should show the speed limit of the road you're on (at the bottom on Tomtom's) and that this is almost always correct (with a big stress on the almost).

Check out the DGN driving school videos. A lot of failures on the mock tests in that youtube channel are down to poor observation.

3 more questions:
- When on a dual carriageway and you have to turn right at the roundabout, let's say 1000 yards from where you are right now, when do you move into the right-hand lane? I have seen videos where the learners move into the right learn too early and hence get a minor for it. Now how many yards from the roundabout should it be when I move into the right lane? And I am saying "1000 yards" as I would be checking the sat nav. Most importantly, as both lanes in a dual carriageway are 40mph, surely it shouldn't matter?
- And what if a driver in front of me is going extremely slow at 30mph on a dual carriageway(lorry for example. Also, this did happen today when I was driving) and I can't turn right as there are fast-travelling traffic already. What should I do- I would just slow down right ?
- When doing the forward bay park, and then you have to reverse backwards out of the bay afterwards, to which limits am I allowed to do so? For example: when I normally reverse back out and start turning, my tyres start the cut the bay lines of the adjacent bays. And when I reverse backwards to the left, my car seems to be in the right hand lane of the road- so how do I fix this (as I reverse the back of my car goes towards the left).

What did your instructor say?

For the dual carriageway turning right lane chage in advance: it all depends. On the speed limit, the traffic around you, especially behind, your speed. It's all down to doing the observations and driving safely without inconveniencing other road users.

Don't be afraid to deliberately go the wrong way, if you never see a safe gap to move into the right hand lane when approaching a roundabout.

In heavy traffic I will quite often go the wrong way, to be ultra cautious and defensive about my lane changes.

For the slow moving lorry, overtake ONLY if it's safe to do so. Anticipation and observation will help avoid this situation more often than not. Even then sometimes you will get stuck behind a slow moving vehicle. That's fine, slow down, leave a safe gap.

Good luck!

I passed !! With 4 minors. Thanks everyone