Hi Lizzie!
Some sound advice given to you already!
Possibly as Observer points out ... you may be giving out the wrong messages to other drivers if split is 50/50. Have a little think about your road position next time you negotiate the roundabout.
It's great that you are thinking about it - and the very act of doing so appears to show the signs of thoughtful expertise and motivation to improve. This canniot be said for you boss and his colleauge according to your post...
OK - I do not know this roundabout - but they all differ and some can be very tricky and confusing. Think we had a debate in the archives somewhere as well - about May -ish.
This advice is given in Road Craft anyway - and this is a good book for you to add to your bookshelf. As you approach any roundabout you are seeking information - identifying hazards. In this case - you have identified the hazard - people in the right hand lane who need some training in mirror work and road space apparently However, one wrong and even two wrongs do not make the proverbial right and you have to observe, anticipate and plan your defensive action accordingly. As you approach this roundabout - scan to the front, sides and rear and consider an over shoulder glance into a blind spot. Decide early which lane to take. In this instance it appears to be 50/50 and perhaps the majority use exit 1 and exit 2 - with some of the outer lane traffic perhaps being right hand turners who entered at the first exit?
If you choose the right hand lane: Keep alert for an early view of traffic both on the roundabout and approaching from other entrances - you approach being prepared to stop but ready to go....
Once on the roundabout - you want L2 - and you then need to adjust your position. This requires impeccable mirror work before committing yourself to your exit... again check your nearside roadspace is clear before you move across. This is what the muppets cutting in on you at exit 2 should be doing in any case. Thus they are not giving you the roadspace and possibly would be liable if they hit you. It is a common headaches for insurance companies to decide on liability in a roundabout collision of this type. Would be up to the insurance company to judge - and I'd keep a disposable camera in the car to take pictures in case of a collsion. It helps!
I would tell your boss and his colleague that driving is an ongoing learning process - and a BiB who is now 50 and is a Daddy Rat is still learning and going on refresher courses - some 26 (ArrgghHHH! NO!) years after qualifying as a Class 1. driver. Tell him that one hopes his mirror work and anticipation of numpties is as up to speed as yours - cos from your post - it does not make me think so. Add that a complacent muppet who thinks he knows it all is far more dangerous than a person with a three year old driving licences who has joined safespeed hall of excellence and bought Road Craft

just has to be safer by default. Or - you could just point him discreetly at this site
If you approach on the left - you would still be watching the antics of the traffic on your right and would have to be prepared to give sufficient signalling and space - in full anticipation that they will wish to take this second exit . Signal your intention and check your road position makes your intention clear as you pass the first exit. I