@CricketCrocket- No, that's the unnecessary social contact group.
Self isolating for 12 weeks is only for those with "serious health conditions". I'm assuming we will be given details on exactly who this is in writing.
But I've linked Boris' speech above, so you can read it and see exactly what he says. To be fair, he doesn't say that they should self isolate, just that they should be "largely shielded".