I’ve skimmed the rest of the posts after this one.
The specific lane is less relevant as it is not a hard rule when driving ahead, though expectations may generally be the left lane unless there are two lanes - but this could result in a 50:50
The lack of indication is a key element.
They weren’t indicating right (from my scan of the rest) which means you don’t know where they are going. This doesn’t absolve you of paying attention
Rule 186 - indicate left and keep left if taking the first exit (does not apply here)
indicate right if turning right or all of the way around
anywhere else, indicate left when passing the previous exit
You ought to be aware that they may have gone ahead, but they ought to have indicated before exiting (they were not required to indicate on approach)
As you appear to have passed to their left (due to your side being clear) and they have caught up then they were not giving due care and attention, we’re not indicating on exit (but you may not have seen by then, (and they should not have relied on you to make any other manouvre (such as getting out of their way)
Providing they went into you then they are at fault
They are also a ‘professional’ and should have a standard to their driving and care for other road users and their passengers
Failing to stop and exchange details is an issue, ensure that the court are aware of your efforts to get this
It sounds like they have been given the chance to come up with a better defence, and ideally it will end in your favour