Yeah definitely look at your mirror loads and make it blatently obvious you are, not just looking at them from the corner of your eye but physically moving your head a bit.
I failed for being too hesistant first time and going round a roundabout in 3rd gear. I was on a long road and I waited for cars that were like 100 metres away lol because I didn't think there was any spaces on my side. The examiner hated me anyway, he kept putting his leg against the gear stick and wouldn't even move it when I tried to change gear. This then made be go around the roundabout in 3rd.
The second examiner was fine, he would ask about my college, my studies, etc. I think having the conversation relaxes you, my answers to his questions were quite vague because I made sure I concentrated as well. He even asked whether I was in his way doing parallel parking.
Always check your blindspot.
Check both side mirrors if you have to do an emergency stop. Brake first, then clutch at the end. I kept doing it the other way around. Don't look behind before you stop because he wouldn't have asked you to do it if there was cars behind you.
When you are doing manoeuvres, keep checking that there aren't cars around. If there are, stop and stare because that is the signal that they could go round you. This means you aren't disrupting them or they won't drive off quickly in impatience and annoy other drivers etc.
Don't start thinking you have failed because he writes things down. I thought I'd failed the second time when I had passed. I spent the last 15 minute not caring and just wanting to get back to the centre.
I think I was asked if I wanted the window open. This could help you if you're nervous if you get quite hot under pressure.
Make sure you go to the toilet before, it could last 20-40 minutes.
Get a good position at the junctions, I tended to get too far back and then have to go forward a metre and then stop again.
Get up the gears quickly. I tended to stay around 25 mph in 3rd but with my second test I went up to 4th a lot more.
Don't be scared to ask what direction or road again.
Also if you see that the roundabout is quite busy then perhaps ask beforehand so you can get into the correct lane. My first test, I was told way too late if it was going to be in the right lane.
Don't get too excited when you are told you are going back to the centre. You can still fail!
Make sure when doing parallel parking that you turn the wheel at the right point. Do it as soon as the back of your car gets past the back of the other car. I sometimes went past the turning point. This could mean some messing about at the end like being paranoid you are too close to the car behind etc. Steering at the right time makes your life so much easier. Also turn the car straight at the last moment so that you are within a foot. I hated parallel parking.
Signal off a roundabout.
Edit: If they don't signal at the roundabout then look at the car position and whether it would tally with being second exit.
Edit 2: Just relax. They are mostly tips that you would know about anyway.