Always have it in your head that on a big roundabout where the lanes are clearly marked for turning left or going straight on... the chances are the buffoon to your left in the straight on lane will be turning right
Especially true with foreign HGV's
Always assume that the guy in front will cut so close to the roundabout centre itself that you won't have any space there either, no matter which lane he starts out in.
Dealing with a busy roundabout actually starts well before you reach it....you need to dominate your space on the road so that all the cars in the area that could affect you KNOW you're there and respect your space.
This then carries on as you enter the roundabout and go round it.....you need to take control of your space, whilst also presuming that others will do stupid things.
It's hard to explain TBH, and there's a fine line between aggressive riding (bad) and assertive riding (good, and necessary) but you'll get that through experience.
You are on a bike bike with big road presence though, so you start off with some advantages.....it's the little things that you will end up doing subconsciously that will make the difference though....making sure you are in the mirror space of anything in front of you (IE making sure you keep out of the blind spots) , pulling into a space in a way that claims it as 'YOURS' without being aggressive, not allowing tempting gaps to appear that some chancer in a car will try and fill, making sure you are in a gear that allows you the best control and chance to accelerate out of trouble etc.
I don't think it's possible to write up a set of instructions to be honest, as every roundabout is different and every set of conditions when you arrive at the roundabout you've done a hundred times will be different, all you can do really is learn through experience, don't be scared of them and learn that all vehicles on the road have a form of 'body language', including your own bike, and you can read that body language instinctively once you've picked up on it.
Sometimes, you'll 'know' that a car is going to do something before it does it.......it's not precognition, its just that you have picked up on the body language of the car.....the way the driver is sitting, the way his head moves (is he watching mirrors etc) the way his wheels move, how steady he is on his line and how smoothly he brakes/accelerates, even what the car looks like (flat cap and cushions on the back shelf, plastic box with gold patterns containing tissues on the back shelf, three oiks smoking and jiggling boisterously around in the back seat etc etc etc)
I can't explain it, it does only come with experience, and although it does sound odd, I truly think that most vehicles have a form of body language that you can tune into and give yourself a headstart in dealing with them, if that makes sense
