I was really lucky and got tickets to see last week's show 29/10.
We were told to be there early and arrived at 2.30pm to be let in at 4.45pm. Some people in front of us got there at 12 noon. We were given numbered stickers when we got in and were 51 and 52 (I think). We got in but some of the people behind us didn't.
It's a real lottery how many public they let in. Most of the seats are used for family/friends of the dancers/celebrities (understandably), and loads of seats were reserved for 'production' people. Out of about 30 on our balcony only about 6 of us were public.
The tickets were advertised on the BBC SCD site and you had to ring up for them. Then it is pure luck if you get sent any tickets as they are sent out randomly to people who applied. I have a relative who works for the BBC but doesn't get any priority over any other public requesting tickets!!