I've driven several different cars and have never had problems judging distance for overtaking until now.

In my current car, other vehicles look super close in my rearview but super far in my side mirror. I can't be sure what's confusing me, but I think there's more of a difference than I've had before. It's like neither one is accurate and both exaggerate.

This isn't a problem for my clearance from parked cars, or parking or whatever, only when changing lanes (especially when moving left, as the windscreen frame is quite obstructing so I have to do a big head turn).

I know I'll get used to it eventually (and have been), but in the meantime I can't exactly experiment on a NSL dual carriageway.

I've been being cautious but have definitely annoyed some people by delaying returning left after overtaking. The one time I took more of a chance (but still thought it was safe), the guy I pulled in front of abruptly changed to the right and honked at me. To be fair, I think he had plenty of time to ease off the accelerator but preferred to give me a scare, but I really didn't think he'd have to do anything or I wouldn't have gone. So now I'm back to being overly cautious.

I find when moving right I've started relying more on my side mirror but still only chance moving over for obviously large gaps. For moving left, I rely more on my rearview and a head turn. (Of course I do a shoulder check moving right as well, just don't need as big a one).

How can I get used to this quickly without taking risks? Which mirror should I most be relying on?