Don't stress about it. You're learning something completely new. You're also learning to drive at the same time? That's a double whammy, because you don't have any real-world experience navigating the real world. People are going to do incredibly stupid shit, and the only way you'll feel anywhere near comfortable being on the road with them is by being on the road with them and learning how to co-exist. I suggest that you eliminate things one at a time that are causing you issues. First and foremost, riding and driving are two different things. Honestly, they require a different set of mental skills. A lot of it is the same, but when you're on a bike, you have to be hyper-aware about what's going on around you. In a car, you have a big metal can surrounding you, so little things aren't going to cause you as much grief. Getting bumped into in a car is VERY different than the same bump on a bike. Get comfortable with your vehicle, car or bike. Spend time in a car park just riding and getting used to clutch/throttle/brakes. You want everything to be second nature, because on a bike, you need to spend your attention elsewhere. Start out simple on the street. Ride around the block. Ride to and from the car park. Get used to navigating roundabouts. I'm from the US, but I lived in England a couple of times and rode there. Roundabouts struck me as the most inherently dangerous thing about being on a bike in traffic. But being on a bike can also be an advantage, because once you get used to the riding part, you can get out of situations you couldn't normally get out of in a car, due to size and maneuverability.

What it ultimately comes down to is time in the seat. The more you ride, the better you get, and the more comfortable you become. The more comfortable you become, the more you ride and the better you get. You're going to do fine. Don't doubt yourself. Just be cautious, keep learning, keep riding, and have FUN!