Many people hear "inside lane" on a motorway and think it's the "fast lane" near the central divider but that's actually the "outside lane". ( source: https://dictionary.cambridge.org/dictionary/english/outside-... ).

But that terminology has been confused over time and so many people get it the wrong way around that the DVLA has stopped using it in the highway code.

So I would suppose 'inside' and 'outside' were also considered relative to the kerb.

In practice, large multi-lane roundabouts in the UK usually have lane markings as you enter, with specific lanes for each exit. In general, so long as you were in the correct lane as you entered the roundabout, the lane markings should guide you to the correct exit and you shouldn’t have to do any filtering.

The problem seems to be that a lane that goes to two places is sometimes marked inconsistently with each of the two places - meaning you think you are in the wrong lane, when you are not.