Roundabouts, giving way & priority

[DaveCWK]

If you are waiting to join a roundabout, and there is a car approaching from a join to the right that is not yet at or on the roundabout, do you have a right of way/priority if you join (i.e cross the white dashed line) the roundabout before them?

[DaveCWK]

SkodaIan said:

Try reading highway code 185:

"When approaching a roundabout, you should:

• Give priority to traffic approaching from your right....."

yeah I was aware of that, but had it in my head there was also a rule to give way to cars already established on a roundabout, So where is the line drawn between the two?